Pharmaceutical piperazine compounds

ABSTRACT

Piperazine derivatives of formula (A): ##STR1## wherein  --------  denotes an optional bond, provided that either  ----   a   ----  and  ----   c   ----  are both bonds and  ----   b   ----  and  ----   d   ----  are not bonds, or  ----   b   ----  and  ----   d   ----  are both bonds and  ----   a   ----  and  ----   c   ----  are not bonds; each of R 14  and R 15  is independently selected from hydrogen and C 1  -C 6  alkyl which is unsubstituted or substituted by an organic functional group; and each of R 1  to R 10 , which may be the same or different, is independently hydrogen or an organic functional group; and the pharmaceutically acceptable salts and esters thereof have utility as modulators of multiple drug resistance (MDR).

The present invention relates to compounds useful as modulators ofmultiple drug resistance (MDR), to their preparation and topharmaceutical and veterinary compositions containing them.

The resistance of tumours to treatment with certain cytotoxic agents isan obstacle to the successful chemotherapeutic treatment of cancerpatients. A tumour may acquire resistance to a cytotoxic agent used in aprevious treatment. A tumour may also manifest intrinsic resistance, orcross-resistance, to a cytotoxic agent to which it has not previouslybeen exposed, that agent being unrelated by structure or mechanism ofaction to any agent used in previous treatments of the tumour.

Analogously, certain pathogens may acquire resistance to pharmaceuticalagents used in previous treatments of the diseases or disorders to whichthose pathogens give rise. Pathogens may also manifest intrinsicresistance, or cross resistance, to pharmaceutical agents to which theyhave not previously been exposed. Examples of this effect includemulti-drug resistant forms of malaria, tuberculosis, leishmaniasis andamoebic dysentery.

The above phenomena are referred to collectively as multi-drugresistance (MDR). As discussed more fully later on, a plasma membraneglycoprotein (P-gp) is implicated in the mechanism which underlies MDR.P-gp has drug binding properties. Certain agents which have the capacityto modulate MDR may therefore also be useful in facilitating thedelivery of drugs across the blood-brain barrier and in treating AIDSand AIDS-related complex.

Disadvantages of drugs which have so far been used to modulate MDR,termed resistance modifying agents or RMAs, are that they frequentlypossess a poor pharmacokinetic profile and/or are toxic at theconcentrations required for MDR modulation.

It has now been found that a series of piperazine derivatives haveactivity as modulators of multiple drug resistance. The presentinvention therefore provides a piperazine of formula (A): ##STR2##wherein ₋₋₋₋₋₋₋₋ denotes an optional bond, provided that either ₋₋₋₋^(a) ₋₋₋₋ and ₋₋₋₋ ^(c) ₋₋₋₋ are both bonds and ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋^(d) ₋₋₋₋ are not bonds, or ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋ ^(d) ₋₋₋₋ are bothbonds and ₋₋₋₋ ^(a) ₋₋₋₋ and ₋₋₋₋ ^(c) ₋₋₋₋ are not bonds; each of R₁₄and R₁₅ is independently selected from hydrogen and C₁ -C₆ alkyl whichis unsubstituted or substituted by a group selected from halogen,optionally substituted phenyl, optionally substituted C₁ -C₆ alkenyl,cyano, hydroxy, --OC(O)R¹¹, --N(R¹¹ R¹²) --CON(R¹¹ R¹²), --COOR¹¹,succinimido, phthalimido, and ##STR3## provided that, when ₋₋₋₋ ^(b)₋₋₋₋ and ₋₋₋₋ ^(d) ₋₋₋₋ are both bonds at least one of R₁₄ and R₁₅ is C₁-C₆ alkyl substituted as defined above; or R₁₄ forms a --CH₂ -- linkageto ring a, thereby completing a 6-membered N-containing heterocycle withthe nitrogen to which it is attached; R₁₆ is C₁ -C₆ alkyl unsubstitutedor substituted either as defined above for R₁₄ and R₁₅ or substituted bya pyridyl group; and each of R₁ to R₁₀, which may be the same ordifferent, is independently selected from hydrogen, C₁ -C₆ alkylunsubstituted or substituted by one or more halogen atoms, C₁ -C₆alkoxy, C₁ -C₆ alkylthio, halogen, hydroxy, nitro, optionallysubstituted phenyl, cyano, --CH₂ OH, --CH₂ COOH, --CO₂ R¹¹, --NHCOR¹¹,--NHSO₂ R¹³, --SO₂ R¹³, --CON(R¹¹ R¹²), --SOR¹³, --SO₂ N(R¹¹ R¹²),--N(R¹¹ R¹²), --O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --OCOR¹¹,--CH₂ OCOR¹¹, --CH₂ NHCOR¹¹, --CH₂ NHCOOR¹³, --CH₂ SR¹¹, --CH₂ SCOR¹¹,--CH₂ S(O)_(m) R¹³ wherein m is 1 or 2, --CH₂ NHCO(CH₂)_(n) CO₂ R¹¹,--N(R¹¹)COR¹², --NHCOCF₃, --NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n)OCOR¹¹ and --NHCO(CH₂)_(n) OR¹¹ ;

wherein n is O or is an integer of from 1 to 6, each of R¹¹ and R¹² isindependently H or C₁ -C₆ alkyl or, when R¹¹ and R¹² are attached to thesame nitrogen atom, they may alternatively form with the nitrogen atom asaturated five or six-membered heterocyclic ring; and R¹³ is C₁ -C₆alkyl; or a pharmaceutically acceptable salt or ester thereof.

In one embodiment the compound is of the following formula (Aa):##STR4## wherein each of R₁ to R₁₀, R₁₄ and R₁₅ is as defined above.

In another embodiment the compound is of the following formula (Ab):##STR5## wherein each of R₁ to R₁₀, R₁₄ and R₁₆ is as defined above.

The numerals 1 to 10 denote ring positions on the phenyl groups informula A. The letters a and b refer to the two phenyl rings themselves.

When ring a or b is substituted phenyl, the benzene ring may besubstituted at any of the ortho, meta and para positions by one or moresubstituents, for example one, two or three substituents, which may bethe same or different, independently selected from the groups specifiedabove for R₁ to R₁₀ other than hydrogen.

A C₁ -C₆ alkyl group may be linear or branched, or may comprise acycloalkyl group. A C₁ -C₆ alkyl group is typically a C₁ -C₄ alkylgroup, for example a methyl, ethyl, propyl, i-propyl, n-butyl,sec-butyl, tert-butyl or cyclopropylmethyl group. A halogen is, forexample, fluorine, chlorine, bromine or iodine. A C₁ -C₆ alkyl groupsubstituted by halogen may be substituted by 1, 2 or 3 halogen atoms. Itmay be a perhaloalkyl group, for example trifluoromethyl.

A C₁ -C₆ alkenyl group is typically a C₁ -C₄ alkenyl group, for instance--CH₂ --CH═CH₂ or --CH₂ --CH═CHCH₃.

A C₁ -C₆ alkoxy group is typically a C₁ -C₄ alkoxy group, for example amethoxy, ethoxy, propoxy, i-propoxy, n-butoxy, sec-butoxy or tert-butoxygroup. A C₁ -C₆ alkylthio group is typically a C₁ -C₄ alkylthio group,for example methylthio, ethylthio, propylthio, i-propylthio,n-butylthio, sec-butylthio or tert-butylthio.

When R¹¹ and R¹² form a heterocyclic group together with the nitrogenatom to which they are attached, it is, for example, anN,N-tetramethylene group.

In compounds of formula A, Aa or Ab free rotation may occur at roomtemperature about the single bonds connecting rings a and b to thedouble bonds at positions 3 and 6 of the 2,5-piperazinedione ring.Positions 2 and 6, and positions 3 and 5, in both rings a and b cantherefore be considered as equivalent. As a consequence the followingpairs of substituents can be viewed as interchangeable: R₁ and R₅ ; R₂and R₄ ; R₆ and R₁₀ ; and R₇ and R₉.

When in formula A ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋ ^(d) ₋₋₋₋ are both bonds, orin formula Aa, one of R₁₄ and R₁₅ is C₁ -C₆ alkyl substituted as definedabove. The other may be hydrogen or C₁ -C₆ alkyl, either unsubstitutedor substituted as defined above. When R₁₄ and R₁₅ are both substitutedC₁ -C₆ alkyl they may be the same or different. Preferred substituted C₁-C₆ alkyl groups for R₁₄ and R₁₅ are C₁ -C₆ alkyl groups substituted byhalogen, phenyl, 4-nitrophenyl, --COOH, --COOMe, --CH₂ --CH═CH--CH₃,--CH₂ --CH═CH₂, --CH₂ CH═CH--CH₂ X, cyano, --OC(O)CH₃ --C(O)NMe,--C(O)NHMe, --C(O)NH₂, ##STR6## and succinimido, wherein X is halogen,particularly bromine. For example, R₁₄ is H or C₁ -C₆ alkyl and R₁₅ is apreferred substituted C₁ -C₆ alkyl group specified above. In oneembodiment R₁₄ is H, Me, or cyclopropylmethyl and R₁₅ is a preferredsubstituted C₁ -C₆ alkyl group specified above.

When in formula A ₋₋₋₋ ^(a) ₋₋₋₋ and ₋₋₋₋ ^(c) ₋₋₋₋ are both bonds, orin formula Ab, R₁₄ is hydrogen, or unsubstituted or substituted C₁ -C₆alkyl as defined above, then R₁₆ is unsubstituted or substituted C₁ -C₆alkyl as defined above. Typically at least one of R₁₄ and R₁₆ is C₁ -C₆alkyl substituted as defined above, for instance R₁₆ is C₁ -C₆ alkylsubstituted as defined above and R₁₄ is unsubstituted alkyl, forinstance Me.

Preferably one of rings a and b is unsubstituted or is mono-substitutedwhilst the other ring is unsubstituted or is substituted at one or moreof positions 2 to 6. The ring which is mono-substituted may carry thesubstituent at any one of positions 2 to 6, for instance position 3 or4, especially position 4. Thus for instance, when ring b ismono-substituted, one of R₆ to R₁₀ is other than hydrogen, preferably R₇or R₈, especially R₈. When ring a is mono-substituted one of R₁ to R₅ isother than hydrogen, preferably R₂ or R₃, especially R₃. When one ofrings a and b is mono-substituted the substituent R₁ to R₅, or R₆ to R₁₀respectively, is preferably selected from a halogen, for instancefluorine; an alkoxy group, for instance OMe; and an acetamido group--NHAc in which Ac denotes acetyl.

When one of rings a and b is unsubstituted, or is mono-substituted asdescribed in the above paragraph, the other ring may bear any desiredsubstitution pattern. For instance, the other ring may be unsubstitutedor may be mono-, di- or tri-substituted at any of positions 2 to 6.

The said other ring may, for instance, be mono-substituted at any ofpositions 2 to 6. It may also be 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or3,5-disubstituted, or 2,3,4-, 2,3,5-, 2,3,6- or 3,4,5-trisubstituted.Thus, when the said other ring is a and is mono-substituted, four of R₁to R₅ are hydrogen and one is other than hydrogen. When the said otherring is ring a and is disubstituted, three of R₁ to R₅ are hydrogen andtwo are other than hydrogen. For example R₁ and R₂, or R₁ and R₃, or R₁and R₄, or R₁ and R₅, or R₂ and R₃, or R₂ and R₄ are other than hydrogenwhilst, in each case, the other three of R₁ to R₅ are hydrogen.

When the said other ring is ring a and is trisubstituted, two of R₁ toR₅ are hydrogen and three are other than hydrogen. For example, R₁, R₂and R₃, or R₁, R₂ and R₄, or R₁, R₂ and R₅, or R₂, R₃ and R₄ are otherthan hydrogen whilst, in each case, the other two of R₁ to R₅ arehydrogen.

When the said ring is b and is mono-substituted, four of R₆ to R₁₀, arehydrogen and one is other than hydrogen. When the said other ring is band is di-substituted, three of R₆ to R₁₀ are hydrogen and two are otherthan hydrogen. For example R₆ and R₇, or R₆ and R₈, or R₆ and R₉, or R₆and R₁₀, or R₇ and R₈, or R₇ and R₉, are other than hydrogen whilst, ineach case, the other three of R₆ to R₁₀ are hydrogen. When the saidother ring is b and is trisubstituted, two of R₆ to R₁₀ are hydrogen andthree are other than hydrogen. For example R₆, R₇ and R₈, or R₆, R₇ andR₉, or R₆, R₇ and R₁₀, or R₇, R₈ and R₉ are other than hydrogen whilst,in each case, the other two of R₆ to R₁₀ are hydrogen.

In a preferred series of compounds of formula A each of R₁ to R₁₀ ishydrogen. In another preferred series of compounds, one of R₆ to R₁₀ isselected from hydroxy, alkoxy, NHCOR¹¹, --CO₂ R¹¹, --N(R¹¹ R¹²),--O(CH₂)_(n) N(R¹¹ R¹²), --SO₂ R¹³, --CON(R¹¹ R¹²), NO₂, --SO₂ N(R¹¹R¹²), --SOR¹³, --N(R¹¹)COR¹² and halogen and the other four of R₆ to R₁₀are H. Alkoxy may be, for instance, OMe or OBu^(n). NHCOR¹¹ is typically--NHAc. CO₂ R¹¹ is typically --COOH or --COOMe. N(R¹¹ R¹²) is typicallyNMe₂ or N,N-tetramethylene. --CON(R¹¹ R¹²) may be --CONH₂. SO₂ R¹³ istypically SO₂ Me, SO₂ N(R¹¹ R¹²) is for example --SO₂ NMe₂. SOR¹³ may beSOMe and --N(R¹¹)COR¹² may be --NMeCOBu^(t). Halogen is typically F orCl. Preferably R₈ is alkoxy, especially OMe or OBu^(n) ; NHCOR¹¹,especially --NHAc; --CO₂ R¹¹, especially --CO₂ H or --CO₂ Me; --CON(R¹¹R¹²) especially --CONH₂ ; NO₂ ; N(R¹¹ R¹²) especially NMe₂ orN,N-tetramethylene; --SOR¹³ especially --SOMe; --SO₂ N(R¹¹ R¹²)especially --SO₂ NMe₂ or halogen, especially F or Cl; and each of R₆,R₇, R₉ and R₁₀, is H.

In the above-mentioned series of preferred compounds R₁ to R₅ are allhydrogen, or one or two of R₁ to R₅ are other than hydrogen whilst theothers are hydrogen. For instance one of R₁ , R₂ and R₃ is other thanhydrogen. Alternatively R₁ and R₃, or R₂ and R₃, are other thanhydrogen. Preferred values for the one or two of R₁ to R₅ which is orare other than hydrogen include alkoxy such as OMe or OBu^(n), halogensuch as Cl or F, hydroxy, --N(R¹¹ R¹²), --CO₂ R¹¹, --CH₂ SCOR¹³, --CH₂SR¹¹, --NHCOR¹¹, --O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --CH₂NHCO(CH₂)_(n) CO₂ R¹¹, --NHCOCH₂ OR¹¹, --NHCOCH₂ OCOR¹³, --CH₂ NHCOOR¹³and CF₃.

In a yet further preferred series one of R₃ and R₈ is alkoxy and theremainder of R₁ to R₁₀ are all H.

Particularly preferred compounds are those wherein R₆, R₇, R₉ and R₁₀are each H, R₈ is selected from H, OMe --NHAc, --CO₂ H, --CO₂ Me,--COHN₂, NO₂, --NMe₂, N,N-tetramethylene, SO₂ Me, --SOMe and --SO₂ NMe₂and each of R₁ to R₅ is as specified above. In these preferred compoundsR₁ to R⁵ are preferably each independently selected from H, halogen,hydroxy, C₁ -C₆ alkoxy, nitro, --CH₂ SCOR¹³, --CH₂ SR₁₁, --CO₂ R¹¹,--OCOR¹³, CF₃, --O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --CH₂NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n) OR¹¹, --N(R¹¹ R¹²),--NHCO(CH₂)_(n) OCOR¹¹, --NHCO(CH₂)_(n) CO₂ R¹¹ and --CH₂ NHCO₂ R¹³ orR₁ and R₂, R₂ and R₃, R₃ and R₄, or R₄ and R₅, form with the carbonatoms to which they are attached an optionally substituted benzene ring.Still more preferably, R₁ and R₂ are independently H, nitro or halogen,R₃ is H, hydroxy, --O(CH₂)_(n) N(R¹¹ R¹²), --OCOR¹³ , --O(CH₂)_(n) CO₂R¹¹, --CH₂ NHCO(CH₂)_(n) CO₂ R¹¹, C₁ -C₆ alkoxy, --NHCO(CH₂)_(n) OR¹¹,--NHCO(CH₂)_(n) OCOR¹¹, --N(R¹¹ R¹²), --CH₂ NHCO₂ R¹³, --CH₂ SR¹¹ or--NHCOR¹¹ ; R₄ is H, halogen, C₁ -C₆ alkoxy, --CH₂ SCOR¹³, --CH₂ SR¹¹ or--CO₂ R¹¹ ; and R₅ is H, nitro or halogen.

In one embodiment R⁸ is NHAc, each of R₆, R₇, R₉ and R₁₀, is H; R₁ is Hor halogen such as Cl or F; R₂ is H, R₃ is halogen such as F or Cl, C₁-C₆ alkoxy such as OMe, --N(R¹¹ R¹²) such as NMe₂ or --NHCOOR¹³ such as--NHCOOBu^(t) ; R₄ is H and R₅ is halogen such as F, Cl, Br, or is CF₃.

In a further embodiment R⁸ is OMe, each of R₆, R₇, R₉ and R₁₀ is H; R¹is H, nitro or halogen such as Cl; R² is H; R³ is H, hydroxy, --OCOR¹³such as OAc, --NHCO(CH₂)_(n) OCOR¹¹ such as --NHCOCH₂ OAc or --NHCOCH₂OR¹¹ such as --NHCOCH₂ OH; R₄ is H and R₅ is H or halogen such as F orCl; or R₂ and R₃ form a benzene ring together with the carbon atoms towhich they are attached.

In a further embodiment each of R₁, R₆, R₇, R₈, R₉ and R₁₀ is H; R₂ isH, --CH₂ SCOR¹³ such as --CH₂ SAc or --CH₂ SR¹¹ such as --CH₂ SH; R₃ is--CH₂ SR¹¹ such as --CH₂ SMe, --CH₂ SCOR¹³ such as --CH₂ SAc,--NHCO(CH₂)_(n) CO₂ R¹¹ such as --NHCO(CH₂)₃ CO₂ Me, --O(CH₂)_(n) CO₂R¹¹ such as --O(CH₂)₄ CO₂ H, --O(CH₂)_(n) N(R¹¹ R¹²) such as --O(CH₂)₃NMe₂, or --N(R¹¹ R¹²) such as --NMe₂ ; and R₄ and R₅ are both H or bothform, together with the carbon atoms to which they are attached, abenzene ring.

Certain diketopiperazines have been disclosed as having utility asbioactive agents. Yokoi et al in J. Antibiotics vol XLI No. 4, pp494-501 (1988) describe structure-cytotoxicity relationship studies on aseries of diketopiperazines related to neihumicin, a compound obtainedfrom the micro-organism Micromonospora neihuensis. Kamei et al in J.Antibiotics vol XLIII No. 8, 1018-1020 disclose that twodiketopiperazines, designated piperafizines A and B, have utility aspotentiators of the cytotoxicity of vincristine.

Examples of specific compounds of the invention are as follows. Thecompound numbering is adhered to in the rest of the specification:

1824(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-(3-phthalimidopropoxy)-3,6-dihydro-2-pyrazinone.

1826(3Z,6Z)-3,6-Dibenzylidene-5-(3-butenyloxy)-1-methyl-3,6-dihydro-2-pyrazinone.

1827(3Z,6Z)-3,6-Dibenzylidene-1-methyl-2-oxo-1,2,3,6-tetrahydro-5-pyrazinyloxyacetonitrile.

1823(3Z,6Z)-3,6-Dibenzylidene-4-methyl-2,5-dioxo-1-piperazinylacetaldehydeethylene acetal.

1822(3Z,6Z)-3,6-Dibenzylidene-1-methyl-2-oxo-1,2,3,6-tetrahydro-5-pyrazinyloxyacetaldehydeethylene acetal.

1818(3Z,6Z)-5-(2-Acetoxyethoxy)-3,6-dibenzylidene-1-methyl-3,6-dihydro-2-pyrazinone.

1820(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-(2-phenethoxy)-3,6-dihydro-2-pyrazinone.

1821(3Z,6Z)-3,6-Dibenzylidene-5-isobutoxy-1-methyl-3,6-dihydro-2-pyrazinone.

1859(3Z,6Z)-3,6-Dibenzylidene-5-(4-bromo-2-butenyloxy)-1-methyl-3,6-dihydro-2-pyrazinone.

1861(3Z,6Z)-3,6-Dibenzylidene-5-(2-butenyloxy)-1-methyl-3,6-dihydro-2-pyrazinone.

1903(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-(4-phthalimidobutoxy)-3,6-dihydro-2-pyrazinone.

1904(3Z,6Z)-5-(4-Acetoxybutoxy)-3,6-dibenzylidene-1-methyl-3,6-dihydro-2-pyrazinone.

1905(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-phthalimidomethoxy-3,6-dihydro-2-pyrazinone.

1902(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-(2-phthalimidoethoxy)-3,6-dihydro-2-pyrazinone.

1901(3Z,6Z)-3,6-Dibenzylidene-1-methyl-5-(4-pyridyl)methoxy-3,6-dihydro-2-pyrazinone.

1863(3Z,6Z)-3,6-Dibenzylidene-5-(2-hydroxyethoxy)-1-methyl-3,6-dihydro-2-pyrazinone.

1864(3Z,6Z)-5-Allyloxy-3,6-dibenzylidene-1-methyl-3,6-dihydro-2-pyrazinone.

1900(3Z,6Z)-3,6-Dibenzylidene-5-(3-dimethylaminopropoxy)-1-methyl-3,6-dihydro-2-pyrazinone.

1819(3Z,6Z)-3,6-Dibenzylidene-5-isopropoxy-1-methyl-3,6-dihydro-2-pyrazinone.

1801(3Z,6Z)-3,6-Dibenzylidene-5-ethoxy-1-methyl-3,6-dihydro-2-pyrazinone.

1825 (3Z,6Z)-1-Allyl-3,6-dibenzylidene-4-methyl-2,5-piperazinedione.

1906 (3Z,6Z)-1,4-Dibenzyl-3,6-dibenzylidene-2,5-piperazinedione.

1936(3Z,6Z)-3,6-Dibenzylidene-1-methyl-4-(3-nitrobenzylidene)-2,5-piperazinedione.

1817(3Z,6Z)-1-(2-Acetoxyethyl)-3,6-dibenzylidene-4-methyl-2,5-piperazinedione.

1803(3Z,6Z)-3,6-Dibenzylidene-1-(2-bromoethyl)-4-methyl-2,5-piperazinedione.

1939(3Z,6Z)-3,6-Dibenzylidene-1-methyl-4-(4-nitrobenzylidene)-2,5-piperazinedione.

1486 Methyl(3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetate.

1614N,N,-Dimethyl-(3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetamide.

1745(3Z,6Z)-6-Benzylidene-5-cyclopropylmethoxy-3-(4-methoxybenzylidene)-1-methyl-3,6-dihydro-2-pyrazinone.

1780(3Z,6Z)3,6-Dibenzylidene)-5-cyclohexylmethoxy-1-methyl-3,6-dihydro-2-pyrazinone.

1612 (3Z)-3-Benzylidene-1,4-dioxo-5(H)-piperazino(1,2-6)isoquinoline.

1527N,N-Diethyl-(3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetamide.

1490 Methyl(3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetate.

1521N,N-Tetramethylene-(3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetamide.

1526N,N-Tetramethylene-(3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetamide.

1454(3Z,6Z)-3-Benzylidene-1-cyclopropylmethyl-6-(4-methoxybenzylidene)-2,5-piperazinedione.

1779 (3Z,6Z)-1-Benzyl-3,6-dibenzylidene-4-methyl-2,5-piperazinedione.

1854(3Z,6Z)-3,6-Dibenzylidene-1-(2-hydroxyethyl)-4-methyl-2,5-piperazinedione.

1856 (3Z,6Z)-3,6-Dibenzylidene-4-methyl-1-phenethyl-2,5-piperazinedione.

1857 (3Z,6Z)-3,6-Dibenzylidene-1-isobutyl-4-methyl-2,5-piperazinedione.

1858((3Z,6Z)-3,6-Dibenzylidene-4-methyl-2,5-dioxo-1-piperazinyl)acetonitrile.

1860(3Z,6Z)-3,6-Dibenzylidene-1-(4-bromoprop-2-enyl)-4-methyl-2,5-piperazinedione.

1862(3Z,6Z)-3,6-Dibenzylidene-1-(but-2-enyl)-4-methyl-2,5-piperazinedione.

1878(3Z,6Z)-1-Benzyl-6-(2,6-dichlorobenzylidene)-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione.

1879(3Z,6Z)-1-Benzyl-6-(4-methoxybenzylidene)-4-methyl-3-(2-nitrobenzylidene)-2,5-piperazinedione.

Compounds of formula A may be prepared by a process which comprisestreating a compound of formula B: ##STR7## with an alkylating agent,typically an alkyl halide, a dialkyl sulphate, or a sulphonate ester,for example a methanesulphonate or p-toluenesulphonate ester in thepresence of a base; to give formula A in which R¹⁵ or R¹⁶ is anunsubstituted C₁ -C₆ alkyl group, and/or, if required, removingoptionally present protecting groups, and/or, if desired, converting onecompound of formula A into another compound of formula A, and/or, ifdesired, converting a compound of formula A into a pharmaceuticallyacceptable salt or ester thereof, and/or, if desired, converting a saltor ester into a free compound, and/or, if desired, separating a mixtureof isomers into the single isomers.

This alkylation can give rise to a mixture of O-alkylated andN-alkylated products, i.e. a mixture of compounds of formula (Aa) and(Ab), as defined above, wherein R₁₅ and R₁₆ are the same. The relativeproportions of the two products will vary depending on the nature of R₁₅and R₁₆, which determines in turn the relative extent of N-alkylationcompared to O-alkylation. The two may be separated by conventionalmethods, for example column chromatography, and obtained separately.

The compound of formula Aa may be prepared by condensing compound offormula (I) ##STR8## wherein R₆ to R₁₀ and R₁₅ are as defined above andare optionally protected, with a compound of formula (II): ##STR9##wherein R₁ to R₅ are defined above and are optionally protected, in thepresence of a base in an organic solvent, thereby obtaining a compoundof formula A in which R₁₄ is hydrogen; or (ii) condensing a compound offormula (I'): ##STR10## wherein R₁ to R₅ and R₁₄ are as defined aboveand are optionally protected, with a compound of formula (III):##STR11## wherein R₆ to R₁₀ are as defined above and are optionallyprotected, in the presence of a base in an organic solvent, therebyobtaining a compound of formula A in which R₁₅ is hydrogen; and, ineither case (i) or (ii), if desired, converting the resulting compoundof formula Aa in which R₁₄ or R₁₅, respectively, is hydrogen into acorresponding compound of formula A in which R₁₄, R₁₅ or R₁₆,respectively, is a C₁ -C₆ alkyl group, by treatment with an alkylatingagent; and/or if required, removing optionally present protecting groupsand/or, if desired, converting one compound of formula A into anothercompound of formula A, and/or, if desired, converting a compound offormula A into a pharmaceutically acceptable salt or ester thereof,and/or, if desired, converting a salt or ester into a free compound,and/or, if desired, separating a mixture of isomers of compounds offormula A into the single isomers.

A compound of formula A produced directly by the condensation reactionbetween (I) and (II) or (I') and (III) may be modified, if desired, byconverting one or more of groups R₁ to R₁₀, into different groups R₁ toR₁₀. These optional conversions may be carried out by methods known inthemselves. For example, a compound of formula A in which one or more ofR₁ to R₁₀ is an ester group may be converted to a compound of formula Awherein the corresponding substituent is a free --COOH group, by acid oralkaline hydrolysis at a suitable temperature, for example from ambienttemperature to 1000° C.

A compound of formula A in which one or more of R₁ to R₁₀ is a --CO₂ Hgroup may be converted into a compound of formula A wherein thecorresponding substituent is esterified by esterification, for exampleby treating the carboxylic acid with a suitable C₁ -C₆ alkyl alcohol inthe presence of 1,3-dicyclohexylcarbodiimide in an inert solvent.

A compound of formula A in which one or more of R₁ to R₁₀ is a free--CO₂ H group may be converted into a compound of formula A in which thecorresponding substituent is a group --CON(R¹¹ R²) , wherein R¹¹ and R¹²are as defined above, for example by treatment with ammonia or an aminein the presence of 1,3-dicyclohexylcarbodiimide in an inert solvent.

A compound of formula A in which one or more of R₁ to R₁₀ is a free--CO₂ H group may be converted into a compound of formula A wherein thecorresponding substituent is a --CH₂ OH group by reduction, for exampleusing borane in a suitable solvent such as tetrahydrofuran.

A compound of formula A in which one or more of R₁ to R₁₀ is a nitrogroup may be converted into a compound of formula A in which thecorresponding substituent is an amino group by reduction under standardconditions, for example by catalytic hydrogenation.

Protecting groups for R₁ to R₁₀ in any of the compounds of formulae (I),(I'), (II) and (III) are optionally introduced prior to step (i) or step(ii) when any of groups R₁ to R₁₀ are groups which are sensitive to thecondensation reaction conditions or incompatible with the condensationreaction, for example a --COOH, --CH₂ OH or amino group. The protectinggroups are then removed at the end of the process. Any conventionalprotecting group suitable for the group R₁ to R₁₀ in question may beemployed, and may be introduced and subsequently removed by well-knownstandard methods.

The condensation reaction between compounds (I) and (II) or (I') and(III) is suitably performed in the presence of a base which is potassiumt-butoxide, sodium hydride, potassium carbonate, sodium carbonate,caesium carbonate, sodium acetate, potassium fluoride on alumina, ortriethylamine in a solvent such as dimethylformamide, or in the presenceof potassium t-butoxide in t-butanol or a mixture of t-butanol anddimethylformamide. The reaction is typically performed at a temperaturefrom 0° C. to the reflux temperature of the solvent.

The alkylation of a compound of formula A wherein R₁₄ or R₁₅ is H iscarried out using an appropriate conventional alkylating agent such as ahaloalkane, for example an iodoalkane, or a dialkylsulphate, in thepresence of a base in an organic solvent. The base may be, for example,sodium hydride, sodium carbonate or potassium carbonate. A suitable baseis then DMF. Another suitable base is aqueous sodium hydroxide, in whichcase a suitable cosolvent is, for example, dioxan, THF or DMF.

The compounds of formula (I) may be prepared by a process comprisingreacting 1,4-diacetyl-2,5-piperazinedione with a compound of formula(III) as defined above, in the presence of a base in an organic solvent,thereby obtaining a compound of formula (I) wherein R₁₅ is hydrogen;and, if desired, treating the resulting compound of formula (I) with analkylating agent to obtain a compound of formula (I) in which R₁₅ is aC₁ -C₆ alkyl group. Similarly, the compounds of formula (I') may beprepared by a process which comprises reacting1,4-diacetyl-2,5-piperazinedione with a compound of formula (II) asdefined above, in the presence of a base in an organic solvent, therebyobtaining a compound of formula (I') in which R₁₄ is hydrogen; and, ifdesired, treating the resulting compound of formula (I') with analkylating agent to obtain a compound of formula (I') in which R₁₄ is aC₁ -C₆ alkyl group.

If necessary, the resulting compound of formula (I) or (I') can beseparated from other reaction products by chromatography.

The reaction of 1,4-diacetyl-2,5-piperazinedione with the compound offormula (III) or (II) is suitably performed under the same conditions asdescribed above for the condensation between compounds (I) and (II), or(I') and (III).

The alkylation of a compound of formula (I) in which R₁₅ is hydrogen, ora compound of formula (I') in which R₁₄ is hydrogen, is suitably carriedout using the same conventional alkylating agents and under the sameconditions as described above for the alkylation of compounds of formula(A) in which R₁₄ is hydrogen. The alkylation step in the case of acompound (I) where R₁₅ is hydrogen typically gives rise to a mixture ofthe compound of formula (I) in which R₁₅ is a C₁ -C₆ alkyl group and itsisomer of the following formula (IV) in which R₁ is a C₁ -C₆ alkylgroup: ##STR12## The alkylation step in the case of a compound (I')where R₁₄ is hydrogen typically gives rise to a mixture of the compoundof formula (I') where R₁₄ is a C₁ -C₆ alkyl group and its isomer offormula (IV') where R₁₄ is a C₁ -C₆ alkyl group: ##STR13## The mixtureof compounds (I) and (IV), where R₁₅ is other than hydrogen, orcompounds (I') and (IV'), where R₁₄ is other than hydrogen, can readilybe separated by chromatography, for example on silica gel. Suitableeluants include ethyl acetate and hexane, or methanol anddichloromethane.

The substituted benzaldehydes of formulae (II) and (III) are knowncompounds or can be prepared from readily available starting materialsby conventional methods. The 1,4-diacetyl-2,5-piperazinedione used as astarting material in the preparation of compounds of formula (I) may beprepared by treating 2,5-piperazinedione (glycine anhydride) with anacetylating agent. The acetylation may be performed using anyconventional acetylating agent, for example acetic anhydride underreflux or, alternatively, acetic anhydride at a temperature below refluxin the presence of 4-dimethylaminopyridine.

Compounds of formula (I) wherein R₁₅ is H may also be prepared by themicrowave irradiation of a mixture comprising1,4-diacetyl-2,5-piperazinedione, a compound of formula (III) andpotassium fluoride on alumina (as base) in the absence of solvent.

Compounds of formula (I) wherein R₁₅ is H may alternatively be prepareddirectly from 2,5-piperazinedione (glycine anhydride) by a process whichcomprises treating the 2,5-piperazinedione with a mixture comprising acompound of formula (III), sodium acetate and acetic anhydride at anelevated temperature, for example under reflux.

Compounds of formula (I') wherein R₁₄ is H may be prepared by analogousprocesses, replacing compound (III) in each case by a compound offormula (II).

Compounds of formula A may also be prepared by a process comprising themicrowave irradiation of (i) a mixture comprising a compound of formula(I) as defined above wherein R₁₅ is H or C₁ -C₆ alkyl, a compound offormula (II) and potassium fluoride on alumina, or (ii) a mixturecomprising a compound of formula (I') wherein R₁₄ is H or C₁ -C₆ alkyl acompound of formula (III) and potassium fluoride on alumina, or (iii) amixture comprising 1,4-diacetylpiperazine-2,5-dione, a compound offormula (II), a compound of formula (III) and potassium fluoride onalumina. The irradiation is performed in the absence of a solvent. Theresulting compound in which R₁₄ and R₁₅ are both H may then be alkylatedusing an appropriate alkylating agent, for example as described above.

Compounds of formula A may also be obtained directly by a process whichcomprises condensing together 1,4-diacetyl-2,5-piperazinedione, acompound of formula (II) and a compound of formula (III) in the presenceof a base in an organic solvent. Suitable bases, solvents and reactionconditions are as described above for the condensation reaction between,for example, compounds (I) and (II).

An alternative direct process for the preparation of compounds offormula A comprises condensing together 2,5-piperazinedione, a compoundof formula (II) and a compound of formula (III) in the presence ofsodium acetate and acetic anhydride at elevated temperature, for exampleunder reflux.

An alternative process for the preparation of compounds of formula (I)comprises treating a compound of formula (V): ##STR14## wherein R₆ toR₁₀ are as defined above, X is a halogen and R' is a C₁ -C₆ alkyl group,with ammonia followed by acetic anhydride.

Compounds of formula (I') may be prepared by an analogous process whichcomprises treating a compound of formula (V'): ##STR15## wherein R₁ toR₅, X and R¹ are as defined above, with ammonia followed by aceticanhydride.

X in formula (V) or (V') is typically iodine. R' is, for example, a C₁-C₄ alkyl group such as a methyl, ethyl, propyl, i-propyl, butyl,sec-butyl or tert-butyl group.

A review of synthetic approaches to unsaturated 3-monosubstituted and3,6-disubstituted-2,5-piperazinediones is provided in Heterocycles,1983, 20, 1407 (C.Shin).

Compounds of formula (A) may be converted into pharmaceuticallyacceptable salts, and salts may be converted into the free compound, byconventional methods. Suitable salts include salts with pharmaceuticallyacceptable inorganic or organic bases, or pharmaceutically acceptableinorganic or organic acids. Examples of inorganic bases include ammoniaand carbonates, hydroxides and hydrogen carbonates of group I and groupII metals such as sodium, potassium, magnesium and calcium. Examples oforganic bases include aliphatic and aromatic amines such as methylamine,triethylamine, benzylamine, dibenzylamine or α-or β-phenylethylamine,and heterocyclic bases such as piperidine, 1-methylpiperidine andmorpholine. Examples of inorganic acids include hydrochloric acid,sulphuric acid and orthophosphoric acid. Examples of organic acidsinclude p-toluenesulphonic acid, methanesulphonic acid, mucic acid andsuccinic acid.

Compounds of formula (A) may also be converted into pharmaceuticallyacceptable esters. Suitable esters include branched or unbranched,saturated or unsaturated C₁ -C₆ alkyl esters, for example methyl, ethyland vinyl esters.

Cancer cells which exhibit multiple drug resistance, referred to as MDRcells, display a reduction in intracellular drug accumulation comparedwith the corresponding drug-sensitive cells. Studies using in vitroderived MDR cell lines have shown that MDR is often associated withincreased expression of a plasma membrane glycoprotein (P-gp) which hasdrug binding properties. P-gp is thought to function as an efflux pumpfor many hydrophobic compounds, and transfection studies using clonedP-gp have shown that its overexpression can confer the MDR phenotype oncells: see, for example, Ann. Rev. Biochem 58 137-171 (1989).

A major function of P-gp in normal tissues is to export intracellulartoxins from the cell. There is evidence to suggest that overexpressionof P-gp may play a clinical role in multiple drug resistance. Increasedlevels of P-gp mRNA or protein have been detected in many forms of humancancers--leukaemias, lymphomas, sarcomas and carcinomas. Indeed, in somecases P-gp levels have been found to increase in tumour biopsiesobtained after relapse from chemotherapy.

Inhibition of P-gp function in P-gp mediated MDR has been shown to leadto a net accumulation of anti-cancer agent in the cells. For example,Verapamil a known calcium channel blocker was shown to sensitise MDRcells to Vinca alkaloids in vitro and in vivo: Cancer Res., 41,1967-1972 (1981). The proposed mechanism of action involves competitionwith the anti-cancer agent for binding to the P-gp. A range ofstructurally unrelated resistance-modifying agents acting by thismechanism have been described such as tamoxifen (Nolvadex:ICI) andrelated compounds, and cyclosporin A and derivatives.

Compounds of formula A and their pharmaceutically acceptable salts andesters (hereinafter referred to as "the present compounds") have beenfound in biological tests to have activity in modulating multiple drugresistance. The results are set out in Example 3 which follows. Thepresent compounds may therefore be used as multiple drug resistancemodifying agents, also termed resistance-modifying agents, or RMAs. Thepresent compounds can modulate, e.g. reduce, or eliminate multiple drugresistance. The present compounds can therefore be used in a method ofpotentiating the cytotoxicity of an agent which is cytotoxic to a tumourcell. Such a method comprises, for instance, administering one of thepresent compounds to the tumour cell whilst the tumour cell is exposedto the cytotoxic agent in question. The therapeutic effect of achemotherapeutic, or antineoplastic, agent may thus be enhanced. Themultiple drug resistance of a tumour cell to a cytotoxic agent duringchemotherapy may be reduced or eliminated.

The present compounds can also be used in a method of treating a diseasein which the pathogen concerned exhibits multi-drug resistance, forinstance multi-drug resistant forms of malaria (Plasmodium falciparum),tuberculosis, leishmaniasis and amoebic dysentery. Such a methodcomprises, for instance, administering one of the present compounds with(separately, simultaneously or sequentially) the drug to which thepathogen concerned exhibits multi-drug resistance. The therapeuticeffect of the drug may thus be enhanced.

A human or animal patient harbouring a tumour may be treated forresistance to a chemotherapeutic agent by a method comprising theadministration thereto of one of the present compounds. The presentcompound is administered in an amount effective to potentiate thecytotoxicity of the said chemotherapeutic agent. Examples ofchemotherapeutic or antineoplastic agents which are preferred in thecontext of the present invention include Vinca alkaloids such asvincristine and vinblastine; anthracycline antibiotics such asdaunorubicin and doxorubicin; mitoxantrone; actinomycin D andplicamycin.

In addition, a human or animal patient suffering from a disease in whichthe responsible pathogen exhibits multi-drug resistance may be treatedfor resistance to a therapeutic agent by a method comprising theadministration thereto of one of the present compounds.

Examples of such disease include multi-drug resistant forms of malaria(Plasmodium falciparum), tuberculosis, leishmaniasis and amoebicdysentery.

MDR modulators also have utility in the delivery of drugs across theblood-brain barrier, and in the treatment of AIDS and AIDS-relatedcomplex. The present compounds can therefore be used in a method offacilitating the delivery of drugs across the blood brain barrier, andin the treatment of AIDS or AIDS-related complex. A human or animalpatient in need of such treatment may be treated by a method comprisingthe administration thereto of one of the present compounds.

The present compounds can be administered in a variety of dosage forms,for example orally such as in the form of tablets, capsules, sugar- orfilm-coated tablets, liquid solutions or suspensions or parenterally,for example intramuscularly, intravenously or subcutaneously. Thepresent compounds may therefore be given by injection or infusion.

The dosage depends on a variety of factors including the age, weight andcondition of the patient and the route of administration. Typically,however, the dosage adopted for each route of administration when acompound of the invention is administered alone to adult humans is 0.001to 10 mg/kg, most commonly in the range of 0.01 to 5 mg/kg, body weight.Such a dosage may be given, for example, from 1 to 5 times daily bybolus infusion, infusion over several hours and/or repeatedadministration.

A piperazine of formula (A) or a pharmaceutically acceptable salt orester thereof is formulated for use as a pharmaceutical or veterinarycomposition also comprising a pharmaceutically or veterinarilyacceptable carrier or diluent. The compositions are typically preparedfollowing conventional methods and are administered in apharmaceutically or veterinarily suitable form. An agent for use as amodulator of multiple drug resistance comprising any one of the presentcompounds is therefore provided.

For example, the solid oral forms may contain, together with the activecompound, diluents such as lactose, dextrose, saccharose, cellulose,corn starch or potato starch; lubricants such as silica, talc, stearicacid, magnesium or calcium stearate and/or polyethylene glycols; bindingagents such as starches, arabic gums, gelatin, methylcellulose,carboxymethylcellulose, or polyvinyl pyrrolidone; disintegrating agentssuch as starch, alginic acid, alginates or sodium starch glycolate;effervescing mixtures; dyestuffs, sweeteners; wetting agents such aslecithin, polysorbates, lauryl sulphates. Such preparations may bemanufactured in known manners, for example by means of mixing,granulating, tabletting, sugar coating, or film-coating processes.

Liquid dispersions for oral administration may be syrups, emulsions andsuspensions. The syrups may contain as carrier, for example, saccharoseor saccharose with glycerol and/or mannitol and/or sorbitol. Inparticular, a syrup for diabetic patients can contain as carriers onlyproducts, for example sorbitol, which do not metabolise to glucose orwhich only metabolise a very small amount to glucose. The suspensionsand the emulsions may contain as carrier, for example, a natural gum,agar, sodium alginate, pectin, methylcellulose, carboxymethylcelluloseor polyvinyl alcohol.

Suspensions or solutions for intramuscular injections may contain,together with the active compound, a pharmaceutically acceptable carriersuch as sterile water, olive oil, ethyl oleate, glycols such aspropylene glycol, and, if desired, a suitable amount of lidocainehydrochloride. Some of the present compounds are insoluble in water.Such compounds may be encapsulated within liposomes.

The following Examples illustrate the invention:

REFERENCE EXAMPLE 1 Preparation of(3Z,6Z)-6-Benzylidene-3-(4-methoxybenzylidene)-2,5-piperazinedione (3)(scheme 1) ##STR16## 1,4-Diacetyl-2,5-piperazinedione (8)

1,4-Diacetyl-2,5-piperazinedione (8) was prepared by the publishedprocedure (S. M. Marcuccio and J. A. Elix, Aust. J. Chem., 1984, 37,1791).

(3Z)-1-Acetyl-3-(4-methoxybenzylidene)-2,5-piperazinedione (9)

(3Z)-1-Acetyl-3-(4-methoxybenzylidene)-2,5-piperazinedione (9) wasprepared by the published procedure (T. Yokoi, L.-M. Yang, T. Yokoi,R.-Y. Wu, and K.-H. Lee, J. Antibiot., 1988, 41, 494).

(3Z,6Z)-6-Benzylidene-3-(4-methoxybenzylidene)-2,5-piperazinedione (3)

A mixture of (3Z)-1-acetyl-3-(4-methoxybenzylidene)-2,5-piperazinedione(9) (1.0 g, 3.6 mmol), benzaldehyde (430 μl, 4.2 mmol) and triethylamine(1.14 ml), 8.2 mmol), in dry DMF (20 ml), was heated at 130° C. for 18h. The reaction mixture was cooled to room temperature and poured intoethyl acetate (100 ml). A yellow solid precipitated which was filteredoff and dried. Yield 360 mg (31%).

C₁₉ H₁₆ N₂ O₃

¹ H nmr (400 MHz d₆ -DMSO): δ: 3.80 (3H, s, O--Me); 6.77 (1H, s, CH═C);6.78 (1H, s, CH═C); 6.98 (2H, d, J=8 Hz, 2×C--H on Ar--OMe) ; 7.30-7.56(7H, m, Ph and 2×C--H on Ar--OMe); 10.15 (2H, br.s, N--H).

¹³ C nmr (100 MHz d₆ -DMSO) δ: 58.68; 117.66; 118.03; 118.77; 128.11;128.92; 129.95; 131.53; 132.11; 132.69; 134.44; 136.59; 161.39; 161.62;162.71.

ms (desorption chemical ionisation, ammonia):

m/z (% relative intensity) : 321 (100) MH⁺.

ir: KBr (diffuse reflectance):

v max (cm⁻¹) : 1620, 1700, 3100, 3220.

Elemental analysis: Calculated for C₁₉ H₁₆ N₂ O₃ : C 71.24, H 5.03, N8.74. Found: C 70.92, H 5.02, N 8.80. C 70.89, H 5.06, N 8.79%

REFERENCE EXAMPLE 2 Preparation of (3Z,6Z)-6-Benzylidene-3-(4-methoxybenzylidene)-2,5-piperazinedione (3)(scheme 2) ##STR17##

Compound 16 is treated with ammonia and subsequently with aceticanhydride to yield 1-acetyl-3-benzylidene-2,5-piperazinedione (18).

Compound 18 is then condensed, in the presence of caesium carbonate ortriethylamine in DMF, with 4-methoxybenzaldehyde to yield compound 3.

REFERENCE EXAMPLE 3 Preparation of1-acetyl-3-benzylidene-2,5-piperazinedione

1,4-Diacetyl-2,5-piperazinedione (25.0 g, 126 mmol), which is compound(8) mentioned in Reference Example 1, was heated at 120°-130° C. in DMF(200 ml) with triethylamine (17.6 ml, 126 mmol) and benzaldehyde (13.0ml, 126 mmol). After 4 h the mixture was cooled to room temperature andpoured into EtOAc (1000 ml), and washed three times with brine. Anysolid formed at this stage was filtered off. The filtrate was dried(MgSO₄) and the solvent removed in vacuo. The residue was recrystallisedfrom EtOAc:Hexane to give 11.78 g (38%) of the title compound as ayellow solid.

¹ H NMR (CDCl₃ 400 MHz) δ=2.69 (3H, s) 4.54 (2H, s) 7.20 (1H, s) 7.40(3H, m), 7.48 (2H, m), 7.93 (1H, br.s)

MS(DCI,NH₃) : 262 (MNH₄ ⁺, 20%), 245 (MH⁺, 53%), 220 (52%), 204 (100%),203 (100%)

    ______________________________________                                        Microanalysis                                                                             C            H      N                                             ______________________________________                                        Calc        63.93        4.95   11.47                                         Found       64.11        5.02   11.41                                                     64.05        4.90   11.44                                         ______________________________________                                    

REFERENCE EXAMPLE 4 Preparation of1-acetyl-3-(4-acetamidobenzylidene)-2,5-piperazinedione

1,4-Diacetyl-2,5-piperazinedione (10.0 g, 50 mmol), prepared by thepublished procedure mentioned in Reference Example 1, was stirred in DMF(40 ml) with 4-acetamidobenzaldehyde (8.24 g, 50 mmol) and triethylamine(7 ml, 50 mmol) and heated to 120° C. After 21/2 h the mixture wascooled to room temperature, diluted with EtOAc (100 ml) and stirredovernight. The solid formed was collected, washed with EtOAc and driedto give 8.46 g (56%) of a yellow solid.

¹ H NMR (CDCl₃ +CF₃ CO₂ H, 400 MHz) δ=2.32 (3H, s) 2.72 (3H, s) 4.68(2H, s) 7.36 (1H, s) 7.45 (2H, d, J=8 Hz) 7.60 (2H, d, J=8 Hz)

    ______________________________________                                        Microanalysis                                                                             C            H      N                                             ______________________________________                                        Calc        59.80        5.02   13.95                                         Found       60.08        5.09   13.89                                                     60.11        5.07   13.86                                         ______________________________________                                    

REFERENCE EXAMPLE 5 Preparation of (3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-1-methyl-2,5-piperazine dione (1) (Scheme 4)##STR18##(3Z)-1-Acetyl-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione (10)and 1-Acetyl-5-methoxy-3-(4-methoxybenzylidene)-3,6-dihydropyrazin-2-one(11)

A mixture of (3Z)-1-Acetyl-3-(4-methoxybenzylidene)-2,5-piperazinedione(9) (2.0 g, 7.3 mmol), methyl iodide (0.46 ml, 7.3 mmol), and sodiumcarbonate (800 mg, 7.5 mmol) in dry DMF (50 ml) was stirred under anatmosphere of dry nitrogen for 3 days. The reaction mixture was thenpoured into ethyl acetate (500 ml) and washed with water (4×100 ml) andbrine. The organic phase was separated, dried (MgSO₄), and the solventremoved in vacuo. The residue was purified by flash chromatography(silica, EtOAc:Hexane, 1:1) to give(3Z)-1-acetyl-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione (10)1.38 g (66%) as a yellow solid and1-acetyl-5-methoxy-3-(4-methoxybenzylidene)-3,6-dihydropyrazin-2-one(11) 248 mg (11.8%) as a bright yellow solid.

(3Z)-1-Acetyl-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione(10):

C₁₅ H₁₆ N₂ O₄

¹ H nmr (400 MHz CDCl₃): δ: 2.63 (3H, s, Ac); 2.95 (3H, s, N--Me); 3.87(3H, s, O--Me); 4.52 (s, 2H, N--CH₂ --CO); 6.93 (2H, d, J=8 Hz,Aromatic); 7.26 (1H, s, C═CH); 7.29 (2H, d, J=8 Hz), Aromatic).

ms (desorption chemical ionisation, ammonia):

m/z (% relative intensity): 306 (34%) MNH₄ ⁺ ; 289 (100%); 216 (14%)

ir : KBr (diffuse reflectance) v_(max) (cm⁻¹): 1690, 1700, 3000.

Elemental analysis: Calculated for C₁₅ H₁₆ N₂ O₄ : C 62.49, H 5.59, N9.72 C 62.48, H 5.58, N 9.68. C 62.51, H 5.65, N 9.67%

1-Acetyl-5-methoxy-3-(4-methoxybenzylidene)-3,6-dihydropyrazin-2-one(11)

C₁₅ H₁₆ N₂ O₄

¹ H nmr (400 MHz CDCl₃): δ: 2.68 (3H, s, Ac); 3.86 (3H, s, Ar--OMe);3.99 (3H, s, O--Me); 4.44 (s, 2H, N--CH₂ --CO); 6.95 (2H, d, J=8 Hz,Ar); 7.32 (1H, s, C═CH); 8.03 (2H, d, J=8 Hz, Ar).

ms (desorption chemical ionisation, ammonia):

m/z (% relative intensity): 289 (100%) MH⁺ ; 247 (14%)

ir : KBr (diffuse reflectance):

v_(max) (cm⁻¹): 1610, 1690, 1700, 1740, 2950.

Elemental Analysis: Calculated for C₁₅ H₁₆ N₂ O₄ : C 62.49, H 5.59, N9.72. C 62.52, H 5.59, N 9.64. C 62.52, H 5.64, N 9.66%

(3Z,6Z)-3-Benzylidene-6-(4-methoxybenzylidene)-1-methyl-2,5-piperazinedione(1

A mixture of(3Z)-1-Acetyl-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione (10)(200 mg, 0.69 mmol) and sodium hydride (60% dispersion in oil, 28 mg,0.69 mmol) in dry DMF (10 ml) was stirred at room temperature for 18 h.Benzaldehyde (71 μl, 0.69 mmol) was then added and the reaction mixturestirred at room temperature for 18 h. It was then diluted with ethylacetate (100 ml) and washed with brine (4×50 ml) . The organic phase wasseparated, dried (MgSO₄), and the solvent removed in vacuo. The residuewas purified by flash chromatography (silica, dichloromethane containing1% MeOH) to give 48 mg (21%) of a yellow solid.

C₂₀ H₁₈ N₂ O₃

¹ H nmr (400 MHz CDCl₃): δ: 3.06 (3H, s, N--Me); 3.87 (3H, s, O--Me);6.93 (2H, d, J=8 Hz, 2×C--H on Ar--OMe); 7.06 (1H, s, Ph--CH═C); 7.23(2H, d, J=8 Hz, 2×C--H on Ar--OMe); 7.27 (1H, s, MeOAr--CH═C); 7.30-7.48(5H, m, Ph); (1H, br.s, N--H).

¹³ C nmr (100 MHz CDCl₃) δ: 36.62; 55.34; 113.86; 116.80; 121.30;126.02; 126.14; 128.47; 128.78; 129.06; 129.45; 131.11; 133.07; 159.66;159.68; 159.95.

ms (desorption chemical ionisation, ammonia): 335 (100%) MH⁺.

ir: KBr (diffuse reflectance): v_(max) (cm⁻¹): 1690, 3000, 3180, 3400.

Elemental analysis: Calculated for C₂₀ H₁₈ H₂ O₃ : O 71.84, H 5.43, N8.38. C 71.81, H 5.31, N 8.31. C 71.80, H 5.25, N 8.31%.

REFERENCE EXAMPLE 6 Preparation of(3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-1,4-dimethyl-2,5-piperazinedione(2) (Scheme 5) ##STR19##(3Z,6Z)-3-Benzylidene-6-(4-methoxybenzylidene)-1,4-dimethyl-2,5-piperazinedione(2)

A mixture of(3Z,6Z)-3-Benzylidene-6-(4-methoxybenzylidene)-2,5-piperazinedione (3)(0.5 g, 1.56 mmol), sodium hydride (60% dispersion in mineral oil, 125mg, 3.1 mmol) and methyl iodide (243 μl, 3.9 mmol) in dry DMF (50 ml)was stirred at room temperature for 4 days. The solvent was then removedin vacuo and the residue purified by flash chromatography (silica,eluting with EtOAc:Hexane, 1:3) to give 220 mg (40%) of compound 2 as ayellow solid.

C₂₁ H₂₀ N₂ O₃

¹ H nmr (400 MHz CDCl₃) δ: 2.95 (3H, s, N--Me); 3.04 (3H, s, N--Me);3.85 (3H, s, O--Me); 6.90 (2H, d, J=8 Hz, 2×C--H on Ar--OMe); 7.19 (1H,s, CH═C); 7.21 (1H, s, CH═C) 7.30-7.56 (7H, m, Ph and 2×C--H onAr--OMe).

ms (desorption chemical ionisation, ammonia):

m/z (% relative intensity): 349 (100) MH⁺.

REFERENCE EXAMPLE 7 Preparation Of Starting Compounds 121 and 122

1-Acetyl-3-benzylidene-2,5-piperazinedione (compound 18 prepared inReference Example 2) was N-methylated by treatment with methyl iodide(2.0 equivalents) in the presence of Na₂ CO₃ (1.0 equivalents) in DMF atroom temperature for 24 hours. The solvent was removed and the residuepurified by flash chromatography. The product1-acetyl-3-benzylidene-4-methyl-2,5-piperazinedione, obtained in 45%yield, was treated with 4-methoxybenzaldehyde (1.0-1.1 equivalents) inthe presence of Cs₂ CO₃ in DMF at 80° C. for 206 hours to give compound121, which is(3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-1-methyl-2,5-piperazinedione,in 35% yield.

By an analogous method, but using benzaldehyde in place of4-methoxybenzaldehyde, compound 122 which is(3Z,6Z)-3,6-dibenzylidene-1-methyl-2,5-piperazinedione was obtained in68% yield.

EXAMPLE 1

Compounds of general formula A were prepared using the starting materialB and alkylation conditions specified in the following Table 1. Furthercompounds were synthesised starting appropriately substituted startingcompounds B: 1803, 1817, 1818, 1820, 1823, 1824, 1827, 1859 and 1863.

                  TABLE 1                                                         ______________________________________                                        Target  Starting   Alkylation                                                 Compound                                                                              Compound B Conditions        Yield                                    ______________________________________                                        1780    Compound 122                                                                             NaH (1.1 eq)      16%                                              (Ref. Ex. 7)                                                                             cyclohexylmethylbromide                                                       DMF, room temperature,                                                        8-10 hours;                                                                   Flash chromatography                                       1801    Compound 122                                                                             NaH (1 eq)        39%                                                         EtI (1 eq)                                                                    DMF, room temp                                                                8-10 hours;                                                                   Flash chromatography                                       1819    Compound 122                                                                             As for 1780, but alkylating                                                                     12%                                                         agent is 2-iodopropane                                     1821    Compound 122                                                                             As for 1780, but alkylating                                                                     27%                                                         agent is isobutyl iodide.                                  1857               Products separated by flash                                                                     36%                                                         chromatography                                             1826    Compound 122                                                                             NaH, (1 eq)       14%                                                         4-bromo-1-butene (1 eq)                                    1881    Compound 122                                                                             DMF, room temp,   23%                                                         4 hrs. Products separated by                                                  flash chromatography                                       1855    Compound 122                                                                             NaH (1 eq)         2.5%                                                       1-bromopentane,                                                               DMF, room temp, 8-10 hours,                                                   then flash chromatography                                  1861    Compound 122                                                                             As for 1855, but alkylating                                                                     14%                                                         agent is crotyl bromide.                                   1862               Products separated by flash                                                                     72%                                                         chromatography                                             1900    Compound 122                                                                             NaH, Cl(CH.sub.2).sub.3 NMe.sub.2.HCl,                                        DMF, 24 hours                                                                 80° C.                                                                 Column chromatography                                                         1:1 EtOAc/MeOH)                                            1901    Compound 122                                                                             NaH, 4-chloromethyl-pyridine,                                                 DMF, 24 hours, room temp.                                                     Column chromatography                                                         1:1 EtOAc/hexane                                           1902    Compound 122                                                                             NaH, N-(2-                                                                    bromoethyl)phthalimide                                                        DMF; recyrstallised from hexane                            1903    Compound 122                                                                             NaH,                                                                          N-(4-bromobutyl)phthalimide,                                                  DMF; column chromatography                                                    1:2 EtOAc/hexane,                                                             recrystallised from EtOAC                                  1904    Compound 122                                                                             NaH,                                                                          4-bromobutyl acetate                                                          DMF;                                                                          column chromatography                                                         1:3 EtOAc/hexane                                           1905    Compound 122                                                                             NaH, N-                                                                       (bromomethyl)phthalimide,                                                     DMF;                                                                          recrystallised from                                                           EtOAc/hexane                                               1932    Compound 122                                                                             (i) NaH, DMF, 10 mins                                                                            7%                                                         (ii) N-(3-chloropropyl)                                                       succinimide), Bu.sub.4 NI, 18 hours,                                          65° C.                                                                 (iii) Column chromatography,                                                  silica, EtOAc:hexane                                                          1:2-2:1                                                    1934    Compound 122                                                                             (i) NaH, DMF, 10 mins                                                         (ii) N-(3)-chloropropyl)                                                      succinimide, Bu.sub.4 NI, 70° C., 18                                   hours                                                                         (iii) Column (silica, EtOAc,                                                  hexane, 1:3-1:1),                                                             recrystallised from                                                           EtOAc/hexane)                                              1935    Compound 122                                                                             (i) NaH, DMF, 10 mins                                                                           33%                                                         (ii) Bu.sub.4 NI, 80° C., 18 hours,                                    N-(3-chloropropyl)isatin                                                      (ii) Column: silica, EtOAc:                                                   hexane 1:4-1:2                                             1936    Compound 122                                                                             (i) NaH, DMF,                                                                 (ii) 0° C., 3-bromomethyl-                                             nitrobenzene, 2 hours                                                         (ii) Column (EtOAc/hexane, 1:3)                            1939    Compound 122                                                                             (i) DMF, NaH (1 eq)                                                           (ii) 0° C., 4-bromomethyl-                                             nitrobenzene (1 eq), 2 hours                                                  (iii) Column, EtOAc/hexane                                 1825    Compound 122                                                                             NaH (1 eq), DMF, 10 mins, allyl                                                                 68%                                                         bromide, r.t. overnight                                    1864                                 29%                                      ______________________________________                                    

EXAMPLE 2 Pharmaceutical Composition

Tablets, each weighing 0.15 g and containing 25 mg of a compound of theinvention can be manufactured as follows:

Composition for 10,000 tablets

compound of the invention (250 g)

lactose (800 g)

corn starch (415 g)

talc powder (30 g)

magnesium stearate (5 g)

The compound of the invention, lactose and half of the corn starch aremixed. The mixture is then forced through a sieve 0.5 mm mesh size. Cornstarch (10 g) is suspended in warm water (90 ml). The resulting paste isused to granulate the powder. The granulate is dried and broken up intosmall fragments on a sieve of 1.4 mm mesh size. The remaining quantityof starch, talc and magnesium stearate is added, carefully mixed andprocessed into tablets.

EXAMPLE 3 Testing of compounds A as modulators of MDR

Materials and Methods

The EMT6 mouse mammary carcinoma cell line and the MDR resistant sublineAR 1.0 were cultured in RPMI 1640 medium containing 10% foetal calfserum and 2 mM glutamine at 37° C. in 5% CO₂ . Cells were passagedbetween 1 in 200 and 1 in 2000 in the case of the parental cell line andbetween 1 in 20 and 1 in 200 in the case of the MDR resistant subline,after trypsinisation (0.25% trypsin, 0.2 gl⁻¹, EDTA).

1. Drug accumulation assay

AR 1.0 cells were seeded into 96 well opaque culture plates (CanberraPackard). The assay medium contained a mixture of tritiated Daunorubicin(DNR), a cytotoxic agent, and unlabelled DNR (0.25μ Ci/ml; 2 μM).Compounds of formula A were serially diluted in assay medium over arange of concentrations from 100 nM to 100 μM. The cells were incubatedat 37° C. for 1 hr before washing and counting of cell associatedradioactivity. Each assay included a titration of the known resistancemodifying agent Verapamil as positive control. Results were expressed as% maximum accumulation where 100% accumulation is that observed in thepresence of 100 μM Verapamil.

The results are set out in the following Tables 2, 3 and 4.

                  TABLE 2                                                         ______________________________________                                                                 MAX                                                                IC50 (μm)                                                                             accumulation                                         Compound No.  Accumulation                                                                             (% 100 μm VRP)                                    ______________________________________                                        1454          10.0       --                                                   1486          50.0       --                                                   1490          30.0       63.6                                                 1500          15.0       91.3                                                 1521          30.0       65.2                                                 1526          --         23.3                                                 1527          40.0       73.9                                                 1614          --         25.0                                                 1745          --         35.0                                                 1747          10.0       100.0                                                1771          70.0       60.0                                                 1779          15.0       --                                                   1780          --         20.0                                                 1801          --         40.0                                                 1803          80.0       50.0                                                 1817          20.0       --                                                   1818           7.0       --                                                   1819          --         23.0                                                 1820          --         34.0                                                 1821          --         35.0                                                 1822           9.0       --                                                   1823           9.0       --                                                   1824           3.0       --                                                   1825          10.0       --                                                   1826          --         40.0                                                 1827          --         35.0                                                 1833          12.0       --                                                   1854          35.0       --                                                   1855          10.0       --                                                   1856          15.0                                                            1857          10.0       --                                                   1858          60.0       --                                                   18S9          15.0       --                                                   1860          10.0       --                                                   1861          --         46.0                                                 1862           8.0       --                                                   1863          10.0       --                                                   1864          --         45.0                                                 1878           5.0       --                                                   1879           2.0       --                                                   1900           3.0       --                                                   1901          12.0       --                                                   1902          11.0       --                                                   1903           9.0       --                                                   1904          --         47.0                                                 1905          --         29.0                                                 1906          --         34.0                                                 1936           2.0       --                                                   1939           4.0       --                                                   ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Compound      Conc Comp Potentiation                                          No.           (μM)   Index                                                 ______________________________________                                        1454          5         10                                                    1500          5, 3, 5, 5                                                                              10, 10, 13, 25                                        1747          5         20                                                    1779          5         40                                                    1823          3         20                                                    1824          3, 3, 5, 5                                                                              60, 80, 80, 400                                       1825          3         15                                                    1833          3         20                                                    ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                                                          TOXICITY                                                                      WITH                                                               COMPOUND   CYTOTOXIC                                   COMPOUND CONC CYTOTOXIC                                                                              TOXICITY   AGENT                                       NO.      AGENT (μg/ml)                                                                            (IC50 μM)                                                                             (IC 50 μM)                               ______________________________________                                        1454     1.00          5.0        0.5                                         1486     1.00          10.0       1.0                                         1490     1.00          30.0       2.0                                         1500     0.50          20.0       2.0                                         1521     1.00          70.0       30.0                                        1527     1.00          40.0       1.5                                         1612     1.00          --         0.0                                         1747     1.00          7.0        0.3                                         1779     1.00          15.0       0.8                                         1817     0.50          20.0       1.5                                         1818     0.50          1.5        0.8                                         1822     0.50          5.0        0.5                                         1823     0.50          30.0       0.7                                         1824     0.50          7.0        0.3                                         1825     0.50          20.0       1.5                                         1833     0.50          9.0        1.0                                         1855     0.50          6.0        0.8                                         ______________________________________                                    

2. Potentiation of Doxorubicin toxicity

Compounds of formula A were examined for their ability to potentiate thetoxicity of doxorubicin in AR 1.0 cells. In initial proliferation assayscompounds were titrated against a fixed concentration of doxorubicin(0.5-1 μM) which alone is non-toxic to AR 1.0 cells. Incubations withdoxorubicin were over a four day period before quantitation ofproliferation using the colorimetric sulphorhodamine B assay (Skehan etal; J. Natl. Cancer Inst. 82 pp 1107-1112 (1990))

Compounds which were shown to be able to sensitise AR 1.0 cells to0.8-1.7 μM doxorubicin without high innate toxicity were selected forfurther study. Cells were cultured for four days with concentrations ofdoxorubicin over the range of 0.5 nM-50 μM in the presence of Verapramilat its maximum subtoxic level determined from previous experiments.Proliferation was quantified as described by Skehan et al, loc cit. TheIC₅₀ (concentration required to reduce proliferation to 50% of theuntreated controls) for doxorubicin alone and with the compound offormula A were derived and used to calculate the potentiation index(PI): ##EQU1##

EXAMPLE 4 Characterization of compounds of formula A

The compounds prepared in Examples 1 to 3 were characterised byconventional mass spectroscopic, microanalytical, proton nmr and i.r.techniques. The results are set out in Table 5.

                                      TABLE 5                                     __________________________________________________________________________                  Mass spec   .sup.1 H nmr                                                      m/z, mass   Solvent                                             Mol. Formula  intensity   δ    Microanalysis                            No.                                                                              (M. Wt)    (mode)      all 400 MHz                                                                              Calc Found                               __________________________________________________________________________    1779                                                                             C.sub.26 H.sub.22 N.sub.2 O.sub.2                                                        395(M+H).sup.+ (100%)                                                                     CDCl.sub.3 C 79.17                                                                            79.12                                                                            79.18                                          (CI,NH.sub.3)                                                                             7.48-7.15(15H, m),                                                                       H 5.62                                                                             5.61                                                                             5.66                                                       6.98-6.40(2H, m),                                                                        N 7.10                                                                             6.99                                                                             7.06                                                       4.75(2H, 3),                                                                  2.95(3H, s)                                         1486                                                                             C.sub.22 H.sub.20 N.sub.2 O.sub.5  = 392                                                 MH.sup.• 393,MNH.sub.4.sup.• 410(10%)                                         CDCl.sub.3 C 67.34                                                                            67.46                                                                            67.26                                          DCI,NH.sub.3                                                                              δ.sub.H :7.98(1H, bs),                                                             H 5.14                                                                             5.02                                                                             5.19                                                       7.48(4H, m),                                                                             N 7.14                                                                             7.11                                                                             7.08                                                       7.38(1H, m),                                                                  7.30(1H, s),                                                                  7.28(2H, m),                                                                  7.05(1H, s),                                                                  6.90(2H, d),                                                                  4.35(2H, s),                                                                  3.87(3H, s)                                                                   3.65(3H, s)                                         1879                      CDCl.sub.3 400, J.sub.z                                                       3.03(3H, s),                                                                  3.86(3H, s),                                                                  4.59(2H, s),                                                                  6.86(2H, m),                                                                  6.93(2H, d),                                                                  7.19(3H, m)                                                                   7.26-7.31(3H,                                                                 multiple peaks),                                                              7.36-7.45,                                                                    (2H, multiple peaks)                                                          7.51(1H, t),                                                                  7.58(1H, t),                                                                  8.12(1H, d).                                        1878                                                                             C.sub.27 H.sub.22 N.sub.2 O.sub.3 Cl.sub.2  = 493                                        493/495 100%/60%                                                                          CDCl.sub.3                                                        510/512 14%/9%                                                                            3.03(3H, s)                                                       DCI NH.sub.3                                                                              3.86(3H, s),                                                                  4.57(2H, s),                                                                  6.89-                                                                         6.95(4H, multiple                                                             signals),                                                                     7.18-                                                                         7.35(overlapping                                                              sample & solvent).                                  1862                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.2                                                        359(H+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 7.42→7.28(10H, m),                                                     7.24→7.17(2H, m)                                                       5.24→5.11(2H, m),                                                      4.13(2H, d),                                                                  2.98(3H, s),                                                                  1.57(3H, d).                                        1860                                                                             C.sub.23 H.sub.21 BrN.sub.2 O.sub.2                                                      479(H+43).sup.+ (9%),                                                                     CDCl.sub.3                                                        439(M+H).sup.+ (96%),                                                                     7.44→7.29(10H, m),                                         437(M+H).sup.+ (91%),                                                                     7.22(2H, s),                                                      357(100%).  5.56→                                                      CI,C.sub.4 H.sub.10                                                                       5.47(1H, m)                                                                   5.42→5.32(1H, m)                                                       4.22(2H, d),                                                                  3.78(2H, d),                                                                  2.98(3H, s)                                         1858                                                                             C.sub.21 H.sub.17 N.sub.3 O.sub.2                                                        361(M+NH.sub.4).sup.+ (48%)                                                               CDCl.sub.3                                                        343(M+H).sup.+ (100%)                                                                     7.49→7.32(10H, m),                                         CI,NH.sub.3 7.27(2H, d),                                                                  4.35(2H, s),                                                                  3.01(3H, s).                                        1856                                                                             C.sub.27 H.sub.24 N.sub.2 O.sub.2                                                        409(m+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 7.43→7.22(10H, m),                                                     7.22-7.10(5H, m)                                                              6.93(2H, d),                                                                  3.86(2H, t),                                                                  2.83(3H, s),                                                                  2.72(2H, t).                                        1854                                                                             C.sub.21 H.sub.20 N.sub.2 O.sub.3                                                        349(H+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 7.44→7.28(10H, m),                                                     7.23(1H, s),                                                                  7.18(1H, s),                                                                  3.73(2H, t),                                                                  3.64→3.58(2H, s, br),                                                  2.99(3H, s),                                                                  2.02→1.91(1H, s, br).                        1825                                                                             C.sub.22 H.sub.20 N.sub.2 O.sub.2                                                        345(M+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 7.42→7.28 (10H, m),                                                    7.20(2H, d),                                                                  5.63→5.52(1H, m),                                                      5.01(1H, d),                                                                  4.77(1H, dd),                                                                 4.21(2H, d),                                                                  2.98(3H, s).                                        1823                                                                             C.sub.24 H.sub.24 N.sub.2 O.sub.4                                                        447(M+C.sub.3 H.sub.7).sup.+ (3%),                                                        CDCl.sub.3                                                        405(M+H).sup.+ (100%)                                                                     7.46→7.28(10H, m),                                         CI,C.sub.4 H.sub.10                                                                       7.18(1H, s),                                                                  7.14(1H, s),                                                                  4.74(1H, t),                                                                  3.90→3.80(2H, m),                                                      3.28→3.17(4H, m),                                                      2.98(3H, s),                                                                  1.89→1.78(2H, m).                            1803                                                                             C.sub.21 H.sub.19 N.sub.3 O.sub.2 Br                                                     428,430(M+NH.sub.4).sup.+,                                                                CDCl.sub.3 C 61.33                                                                            61.32                                                                            61.28                                          411,413(M+H).sup.+                                                                        7.38→7.22(10H, m),                                                                H 4.66                                                                             4.70                                                                             4.62                                           CI,NH.sub.3 7.14(2H, s),                                                                             N 6.81                                                                             6.72                                                                             6.66                                                       3.85(2H, t),                                                                             Br                                                                              19.43                                                                            19.32                                                                            19.06                                                      3.33(2H, t),                                                                  2.92(3H, s).                                        1614                                                                             C.sub.23 H.sub.23 N.sub.3 O.sub.4 = 405                                                  MH.sup.• 406                                                                        CDCl.sub.3                                                        DCI NH.sub.3                                                                              δ.sub.H :8.02(1H, bs),                                                  7.45(4H, m),                                                                  7.40(3H, m),                                                                  7.22(1H, s),                                                                  7.05(1H, s),                                                                  6.95(2H, d),                                                                  4.48(2H, s),                                                                  4.35(3H, s),                                                                  2.88(3H, s),                                                                  2.65(3H, s).                                        1527                                                                             C.sub.25 H.sub.27 N.sub.3 O.sub.4 mw = 433                                               434(m.sup.+, 100%)                                                                        CDCl.sub.3                                                        361(12%)    0.83(3H, t),                                                      DCI-NH.sub.3                                                                              1.05(3H, t),                                                                  2.87(2H, δ),                                                            3.25(2H, δ),                                                            3.81(3, H, s),                                                                4.42(2H, s),                                                                  6.98(2H, d),                                                                  7.00(1H, s),                                                                  7.28(1H, s),                                                                  7.30-7.42(7H, m),                                                             7.98(1H, bs).                                       1526                                                                             C.sub.25 H.sub.25 N.sub.3 O.sub.4 mw = 431                                               432(m.sup.+ H, 100%),                                                                     CDCl.sub.3                                                        361(15%)    1.69-1.80(4H, m),                                                 DCI-NH.sub.3                                                                              2.78(2H, t)                                                                   3.33(2H, t),                                                                  3.80(3H, s),                                                                  4.33(2H, s),                                                                  6.96(2H, d),                                                                  7.00(1H, s),                                                                  7.25(1H, s),                                                                  7.27-7.40(4H, m),                                                             8.01(1H, bs).                                       1521                                                                             C.sub.25 H.sub.25 N.sub.3 O.sub.4 = 431                                                  MH.sup.• 432                                                                        CDCl.sub.3 C 69.59                                                                            69.43                                                                            69.52                                          DCINH.sub.3 δ.sub.H :7.98(1H, bs),                                                             H 5.84                                                                             5.67                                                                             5.67                                                       7.45(4H, m),                                                                             N 9.74                                                                             9.63                                                                             9.63                                                       7.34 (3H, m),                                                                 7.25(1H, s),                                                                  7.05(1H, s),                                                                  6.95(2H, d),                                                                  4.37(2H, s),                                                                  3.85(3H, s),                                                                  3.40(2H, t),                                                                  3.00(2H, t),                                                                  1.85(2H, m),                                                                  1.78(2H, m).                                        1490                                                                             C.sub.22 H.sub.20 N.sub.2 O.sub.5 mw = 392                                               393(m.sup.+ H, 100%),                                                                     CDCl.sub.3 C 67.34                                                                            66.86                                                                            66.98                                          410(mNH.sup.4+, 5%)                                                                       3.65(3H, s),                                                                             H 5.14                                                                             5.18                                                                             5.12                                           DCI,NH.sub.3                                                                              3.86(3H, s),                                                                             N 7.14                                                                             7.03                                                                             7.01                                                       4.25(2H, s),                                                                  6.96(2H, d),                                                                  7.02(1H, s),                                                                  7.25-7.42(8H, m).                                   1499                                                                             C.sub.21 H.sub.18 N.sub.2 O.sub.5 mw = 378                                               396(mNH.sup.4+, 8%),                                                                      CDCl.sub.3 +drop TFA                                                                     C 66.66                                                                            66.52                                                                            66.57                                          379(m.sup.+ H, 100%)                                                                      3.90(3H, s),                                                                             H 4.79                                                                             4.75                                                                             4.75                                           DCI-NH.sub.3                                                                              4.40(2H, s),                                                                             N 7.40                                                                             7.33                                                                             7.36                                                       7.00(2H, d),                                                                  7.21(1H, s),                                                                  7.30-7.50(8H, m).                                   1817                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.4                                                        408(m+NH.sub.4).sup.+ (5%),                                                               CDCl.sub.3                                                        391(m+H).sup.+ (100%)                                                                     7.44→7.28(9H, m),                                          CI,NH.sub.3 7.27(1H, s),                                                                  7.21(1H, s),                                                                  7.15(1H, s),                                                                  4.11(2H, t)                                                                   3.80(3H, t),                                                                  2.98(3H, s),                                                                  1.96(3H, s).                                        1747                                                                             C.sub.24 H.sub.24 N.sub.2 O.sub.2=388                                                    MH.sup.+ (100%)-389                                                                       7.40-7.30(m, 7H),                                                                        C 74.21                                                                            73.95                                                                            74.20                                          Also 333, 305, 257                                                                        7.19(s, 1H),                                                                             H 6.23                                                                             6.24                                                                             6.28                                           All < 10%   7.11(s, 1H),                                                                             N 7.21                                                                             7.15                                                                             7.26                                           DCI/NH.sub.3                                                                              6.92(d, 2H)                                                                   3.85(s, 3H),                                                                  3.52(d, 2H),                                                                  3.00(s, 3H),                                                                  1.01(m, 1H),                                                                  0.48(m, 2H),                                                                  0.09(m, 2H)                                         1833                                                                             C.sub.24 H.sub.24 N.sub.2 O.sub.3 = 388Da                                                389Da 100%  CDCl.sub.3 C 74.21                                                                            74.20                                                                            74.17                                          DCI NH.sub.3                                                                              0.09(2H, m),                                                                             H 6.23                                                                             6.95                                                                             6.90                                                       0.37(2H, m),                                                                             N 7.21                                                                             6.57                                                                             6.53                                                       1.00(1H, m),                                                                  3.05(3H, s),                                                                  3.49(2m, d),                                                                  3.35(3H, s),                                                                  6.42(2H, d),                                                                  7.16(2H, d),                                                                  7.27-7.40                                                                     (multiple signals                                                             solvent & sample)                                   1454                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.3                                                        375(mH.sup.+, 100%)                                                                       0.10(2H, m),                                                                             C 73.78                                                                            72.95                                                                            73.17                                          DCI NH.sub.3                                                                              0.39(2H, m),                                                                             H 5.92                                                                             5.94                                                                             5.96                                                       1.05(1H, m),                                                                             N 7.48                                                                             7.42                                                                             7.44                                                       3.58(2H, d, J=6Ht),                                                           3.86(3H, s),                                                                  6.90(2H, d, J=7H.sub.z),                                                      7.05(1H, s),                                                                  7.20(1H, s),                                                                  7.28(2H, d, J=7H.sub.z),                                                      7.35(1H, m),                                                                  7.40(4H, m),                                                                  7.87(1H, br, s)                                     1500                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.3 mw = 374                                               375(m.sup.+ H, 100%)                                                                      0.02-0.08(2H, m),                                                                        C 73.78                                                                            73.59                                                                            73.56                                          DCI NH.sub.3                                                                              0.43-0.47(2H, m),                                                                        H 5.92                                                                             5.77                                                                             5.90                                                       0.95-1.04(1H, m),                                                                        N 7.48                                                                             7.46                                                                             7.44                                                       3.55(2H, d),                                                                  3.85(3H, s),                                                                  6.98(2H, d),                                                                  7.02(1H, s),                                                                  7.22(1H, s),                                                                  7.30-7.40(7H, m),                                                             7.94(1H, broad s).                                  1780                                                                             C.sub.26 H.sub.28 N.sub.2 O.sub.2                                                        401(m+H).sup.+ (100%)                                                                     8.08(2H, d),                                                                             C 77.97                                                                            77.76                                                                            78.06                                          CI,NH.sub.3 7.45-7.22(9H, m),                                                                        H 7.05                                                                             7.03                                                                             7.05                                                       6.85(1H, s),                                                                             N 6.99                                                                             6.93                                                                             6.95                                                       4.25(2H, d),                                                                  2.98(3H, s),                                                                  2.01-1.68(6H, m)                                                              1.40-1.09(5H, m).                                   1818                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.4                                                        391(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 70.75                                                                            70.37                                                                            70.31                                          CI,NH.sub.3 8.03(2H, d),                                                                             H 5.68                                                                             5.75                                                                             5.71                                                       7.42-7.22(9H, m),                                                                        N 7.17                                                                             6.99                                                                             6.99                                                       6.88(1H, s),                                                                  4.65-4.60(2H, m),                                                             4.53→4.48(2H, m),                                                      2.98(3H, s),                                                                  2.11(3H, s).                                        1819                                                                             C.sub.22 H.sub.22 N.sub.2 O.sub.3                                                        347(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 76.28                                                                            75.86                                                                            75.62                                          CI,NH.sub.3 8.03(2H, d),                                                                             H 6.40                                                                             6.37                                                                             6.35                                                       7.40→7.18(9H, m),                                                                 N 8.09                                                                             8.02                                                                             7.92                                                       6.42(1H, s),                                                                  5.12(1H, m),                                                                  3.41(3H, s),                                                                  1.04(6H, d),                                        1820                                                                             C.sub.27 H.sub.24 N.sub.2 O.sub.2                                                        409(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 79.39                                                                            79.23                                                                            79.20                                          CI,NH.sub.3 8.08(2H, d),                                                                             H 5.92                                                                             5.90                                                                             5.83                                                       7.48-7.19(14H, m),                                                                       N 6.86                                                                             6.83                                                                             6.83                                                       6.82(1H, s),                                                                  4.67(2H, 5),                                                                  3.19(2H, t),                                                                  2.98(3H, s).                                        1821                                                                             C.sub.23 H.sub.24 N.sub.2 O.sub.2                                                        361(m+H).sup.+ 100%                                                                       CDCL.sub.3                                                        CI,C.sub.4 H.sub.10                                                                       8.08(2H, d),                                                                  7.42→7.21(9H, m),                                                      6.88(1H, s),                                                                  4.22(2H, d),                                                                  2.98(3H, s),                                                                  2.22(1H, m),                                                                  1.11(6H, d)                                         1822                                                                             C.sub.22 H.sub.24 N.sub.2 O.sub.4                                                        405(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 71.27                                                                            71.12                                                                            71.06                                          CI,NH.sub.3 8.08(2H, d),                                                                             H 5.98                                                                             5.99                                                                             5.99                                                       7.42→7.21(9H, m),                                                                 N 6.93                                                                             6.81                                                                             6.82                                                       6.87(1H, s),                                                                  5.13(1H, t),                                                                  4.61(2H, t),                                                                  4.05→3.99(2H, m)                                                       3.93→3.86(2H, m)                                                       2.97(3H, s),                                                                  2.26(2H, dt)                                        1824                                                                             C.sub.30 H.sub.25 N.sub.3 O.sub.4                                                        492(m+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 8.04(2H, d),                                                                  7.87-7.78(2H, m),                                                             7.71-7.62(2H, m),                                                             7.45→7.23(7H, m),                                                      7.16(2H, d),                                                                  6.80(1H, s),                                                                  4.51(2H, t),                                                                  3.96(2H, t),                                                                  2.94(3H, s),                                                                  2.30(2H, m).                                        1826                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.2                                                        359(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 77.07                                                                            76.94                                                                            76.96                                          CI,NH.sub.3 8.07(2H, d),                                                                             H 6.19                                                                             6.16                                                                             6.15                                                       7.40→7.22(9H, m),                                                                 N 7.82                                                                             7.80                                                                             7.80                                                       6.88(1H, s),                                                                  5.99→5.88(1H, sym m),                                                  5.23(1H, d),                                                                  4.50(2H, t),                                                                  2.98(3H, s),                                                                  2.64(2H, q).                                        1827                                                                             C.sub.21 H.sub.17 N.sub.3 O.sub.2                                                        344(m+H).sup.+ (100%)                                                                     CDCl.sub.3 C 73.45                                                                            72.85                                                                            72.94                                          CI,NH.sub.3 8.00(2H, d),                                                                             H 4.99                                                                             4.94                                                                             4.96                                                       7.45-7.30(7H, m),                                                             7.29→7.22(2H, m),                                                      6.87(1H, s),                                                                  5.07(2H, s),                                                                  3.00(3H, s).                                        1855                                                                             C.sub.24 H.sub.26 N.sub.2 O.sub.2                                                        375(m+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI,NH.sub.3 8.14(2H, d),                                                                  7.40→7.20(9H, m),                                                      6.43(1H, s),                                                                  4.12(2H, t),                                                                  3.42(3H, s),                                                                  1.46(2H, app quin),                                                           1.37-1.28(2H, m),                                                             0.99→0.92(2H, m),                                                      0.81(3H, t)                                         1859                                                                             C.sub.23 H.sub.21 BrN.sub.2 O.sub.2                                                      439(m+H).sup.+ (15%),                                                                     CDCl.sub.3                                                        437(m+H).sup.+ (12%),                                                                     8.04(2H, d),                                                      303(100%)   7.42→7.22(9H, m),                                          CI,NH.sub.3 6.89(1H, s),                                                                  6.18→6.05(2H, m),                                                      4.97(2H, d),                                                                  4.01(2H, d),                                                                  2.98(3H, s).                                        1861                                                                             C.sub.23 H.sub.22 N.sub.2 O.sub.2                                                        359(m+H).sup.+ (100%),                                                                    CDCl.sub.3                                                        303(35%)    8.10→8.02(2H, m),                                          CI,NH.sub.3 7.42→7.20(9H, m),                                                      6.89(1H, s),                                                                  6.5.87→5.77(2H, m),                                                    4.88(2H, d),                                                                  2.98(3H, s),                                                                  1.82→1.78(3H, m).                            1863                                                                             C.sub.21 H.sub.20 N.sub.2 O.sub.3                                                        349(mH.sup.+, 100%),                                                                      CDCl.sub.3                                                        304(5%)     8.02(2H, d),                                                      DCI NH.sub.3                                                                              7.42→7.21(9H, m),                                                      6.41(1H, s),                                                                  4.61→4.55(2H, m),                                                      4.10→4.03(2H, m),                                                      2.97(3H, s),                                                                  2.12→1.91(1H, s, br)                         1864                                                                             C.sub.22 H.sub.20 N.sub.2 O.sub.2                                                        345(mH.sup.+, 100%)                                                                       CDCl.sub.3 C 76.72                                                                            76.77                                                                            76.62                                          303(20%)    8.05(2H, d),                                                                             H 5.85                                                                             3.82                                                                             5.83                                           DCI NH.sub.3                                                                              7.42→7.22(9H, m),                                                                 N 8.14                                                                             8.14                                                                             8.14                                                       6.91(1H, s),                                                                  6.22→6.10(1H, m),                                                      5.49(1H, d),                                                                  5.34(1H, d),                                                                  4.95(2H, d),                                                                  2.98(3H, s).                                        1771                                                                             C.sub.20 H.sub.18 N.sub.2 O.sub.2 = 318                                                  mH+(100%)-319                                                                             CDCl.sub.3                                                        DCI/NH.sub.3                                                                              8.10(d, 2H),                                                                  7.42-7.30(m, 8H),                                                             7.25(s, 1H),                                                                  6.88(s, 1H),                                                                  4.07(s, 3H),                                                                  2.99(s, 3H).                                        1801                                                                             C.sub.21 H.sub.20 N.sub.2 O.sub.2                                                        333(m+H).sup.+ (100%)                                                                     CDCl.sub.3                                                        CI.sub.6, NH.sub.3                                                                        8.08(2H, d),                                                                  7.42→7.22(9H, m),                                                      6.88(1H, s),                                                                  4.51(2H, q),                                                                  2.99(3H, s),                                                                  1.51(3H, t).                                        1745                                                                             C.sub.24 H.sub.24 N.sub.2 O.sub.3 = 388                                                  mH.sup.+ (100%)-389                                                                       CDCl.sub.3 C 74.21                                                                            73.99                                                                            73.95                                          Also,       8.03(d, 2H),                                                                             H 6.23                                                                             6.19                                                                             6.22                                           333(20%), 305(10%),                                                                       7.37-7.27(m, 5H),                                                                        N 7.21                                                                             7.17                                                                             7.18                                           292(10%,    7.23 (5, 1H),                                                     257(10%).   6.91(d, 2H),                                                      DCI,NH.sub.3                                                                              6.90(s, 1H),                                                                  4.28(d, 2H),                                                                  3.85(s, 3H),                                                                  2.98(s, 3H),                                                                  1.38(m, 1H),                                                                  0.68(m, 2H),                                                                  0.43(m, 2H).                                        1939                                                                             C.sub.26 H.sub.21 N.sub.3 O.sub.4 = 439                                                  mH.sup.+ (100%)-440                                                                       CDCl.sub.3                                                        mNH.sub.4 +(20%)-457                                                                      8.08(d, 2H),                                                      CI/NH.sub.3 7.45-7.32(m, 10H),                                                            7.26(s, 1H),                                                                  7.23(s, 1H),                                                                  7.08(d, 2H),                                                                  4.85(s, 2H),                                                                  2.98(s, 3H).                                        1936                                                                             C.sub.26 H.sub.21 N.sub.3 O.sub.4 = 439                                                  mH.sup.+ (100%)-440                                                                       CDCl.sub.3 C 71.06                                                                            70.79                                                                            70.97                                          mNH.sub.4.sup.+ (60%)-457                                                                 8.05(d, 1H),                                                                             H 4.82                                                                             4.88                                                                             4.83                                           Also-305(30%)                                                                             7.70(s, 1H),                                                                             N 9.56                                                                             9.45                                                                             9.49                                           CI/NH.sub.3 7.42-7.21(m, 14H),                                                            4.85(s, 2H),                                                                  2.97(s, 3H)                                         1906                                                                             C.sub.32 H.sub.26 N.sub.2 O.sub.2                                                                    CDCl.sub.3 C 81.68                                                                            81.05                                                                            81.03                                                      7.44-7.35(m, 10H),                                                                       H 5.57                                                                             5.64                                                                             5.63                                                       7.19(s, 2H),                                                                             N 5.95                                                                             5.82                                                                             5.82                                                       7.18-7.07(m, 6H),                                                             6.88(m, 4H),                                                                  4.67(4H).                                           1905                                                                             C.sub.26 H.sub.21 N.sub.3 O.sub.4 = 463                                                  116(25%),   CDCl.sub.3                                                        160(100%),  δ:8.08(2H, d),                                              303(30%),   7.98(2H, m),                                                      m⊕463(30%)                                                                            7.85(2H, m),                                                      Desorption chemical                                                                       7.35(9H, m),                                                      ionisation ammonia                                                                        6.78(1H, s),                                                                  6.08(2H, s),                                                                  2.95(3H, s)                                         1904                                                                             C.sub.25 H.sub.26 N.sub.2 O.sub.4 = 418                                                  43(30%),    CDCl.sub.3                                                        115(80%),   δ:1.88(2H, m),                                              m.sup.• 418 (100%)                                                                  1.95(2H, m),                                                      Desorption chemical                                                                       2.05(3H, s),                                                      ionisation ammonia                                                                        2.98(3H, s),                                                                  4.20(2H, t),                                                                  4.45(2H, t),                                                                  6.88(1H, s),                                                                  7.35(9H, m),                                                                  8.08(2H, d).                                        1903                                                                             C.sub.31 H.sub.27 N.sub.3 O.sub.4 = 505                                                  116(40%),   CDCl.sub.3 C 73.65                                                                            73.46                                                                            73.38                                          160(100%),  δ:1.95(4H, m),                                                                     H 5.38                                                                             5.44                                                                             5.37                                           202(90%),   2.98(3H, s),                                                                             N 8.31                                                                             8.16                                                                             8.15                                           303(30%),   3.85(2H, m),                                                      m.sup.• 505 (50%)                                                                   4.48(2H, m),                                                      Desorption chemical                                                                       6.88(1H, s),                                                      ionisation ammonia                                                                        7.30(9H, m),                                                                  7.80(2H, m),                                                                  7.85(2H, m),                                                                  8.05(2H, d).                                        1902                                                                             C.sub.29 H.sub.23 N.sub.3 O.sub.4 = 477                                                  130(30%),   δ:8.00(2H, d),                                                                     C 72.94                                                                            72.91                                                                            72.92                                          174(100%),  7.80(2H, m),                                                                             H 4.85                                                                             4.82                                                                             4.78                                           303(10%),   7.70(2H, m),                                                                             N 8.80                                                                             8.71                                                                             8.71                                           mH.sup.• 477 (20%)                                                                  7.35(9H, m),                                                      Desorption chemical                                                                       6.85(1H, s),                                                      ionisation ammonia                                                                        4.68(2H, t),                                                                  4.20(2H, t),                                                                  2.98(3H, s)                                         1901                                                                             C.sub.25 H.sub.21 N.sub.3 O.sub.2 = 395                                                  mH.sup.• 396 (100%)                                                                 δ:8.45(2H, d),                                              Desorption chemical                                                                       7.35(10H, m),                                                     ionisation ammonia                                                                        7.26(1H, s),                                                                  7.20(1H, s),                                                                  6.85(2H, d),                                                                  4.78(2H, s),                                                                  3.00(3H, s)                                         1900                                                                             C.sub.24 H.sub.27 N.sub.3 O.sub.2 = 389                                                  305(50%),   CDCl.sub.3                                                        376(100%),  δ:2.28(6H, s),                                              mH.sup.• 390(70%)                                                                   2.45(2H, t),                                                      Desorption chemical                                                                       2.87(3H, s),                                                      ionisation ammonia                                                                        3.65(2H, t),                                                                  4.49(2H, t),                                                                  6.88(1H, s),                                                                  7.32(9H, m),                                                                  8.08(2H, d)                                         __________________________________________________________________________

We claim:
 1. A compound which is selectedfrom:(3Z,6Z)-3,6-Dibenzylidene-4-methyl-2,5-dioxo-1-piperazinylpropionaldehydeethylene acetal; methyl-3,6-dihydro-2-pyrazinone;(3Z,6Z)-1-Allyl-3,6-dibenzylidene-4-methyl-2,5-piperazinedione;(3Z,6Z)-1,4-Dibenzyl-3,6-dibenzylidene-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-1-methyl-4-(3-nitrobenzylidene)-2,5-piperazinedione;(3Z,6Z)-1-(2-Acetoxyethyl)-3,6-dibenzylidene-4-methyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-1-(2-bromoethyl)-4-methyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-1-methyl-4-(4-nitrobenzylidene)-2,5-piperazinedione;Methyl(3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetate;N,N-Dimethyl-((3Z,6Z)-3-benzylidene-6-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinyl)acetamide;N,N-Diethyl-(3Z,6Z)-6-benzylidene-3-(4-methoxybenzylidene)-2,5-dioxo-1-piperazinylacetamide;(3Z,6Z)-1-Benzyl-3,6-dibenzylidene-4-methyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-1-(2-hydroxyethyl)-4-methyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-4-methyl-1-phenethyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-4-methyl-2,5-dioxo-1-piperazinylacetonitrile;(3Z,6Z)-3,6-Dibenzylidene-1-(4-bromobut-2-enyl)-4-methyl-2,5-piperazinedione;(3Z,6Z)-3,6-Dibenzylidene-1-(but-2-enyl)-4-methyl-2,5-piperazinedione;(3Z,6Z)-1-Benzyl-6-(2,6-dichlorobenzylidene)-3-(4-methoxybenzylidene)-4-methyl-2,5-piperazinedione;(3Z,6Z)-1-Benzyl-6-(4-methoxybenzylidene)-4-methyl-3-(2-nitrobenzylidene)-2,5-piperazinedione;and the pharmaceutically acceptable salts thereof.
 2. A compoundselected from the group consisting of a piperazine of formula (Aa):##STR20## wherein each of R₁₄ and R₁₅ is independently selected fromhydrogen and C₂ -C₆ alkyl which is unsubstituted or substituted by agroup selected from halogen, phenyl, C₁ -C₆ alkenylene, cyano, hydroxy,--OC(O)R₁₁, --N(R₁₁ R₁₂), --CON(R₁₁ R₁₂), --COOR₁₁, a groupsuccinimidyl, phthalimidyl or ##STR21## provided that at least one ofR₁₄ and R₁₅ is C₁ -C₆ alkyl substituted as defined above; and each of R₁to R₁₀, which may be the same or different, is independently selectedfrom hydrogen, C₁ -C₆ alkyl unsubstituted or substituted by one or morehalogen atoms, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen, hydroxy, nitro,phenyl, cyano, --CH₂ OH, --CH₂ COOH, --CO₂ R₁₁, --NHCOR¹¹, --NHSO₂ R¹³,--SO₂ R¹³, --CON(R¹¹ R¹²), --SOR¹³, --SO₂ N(R¹¹ R¹²), --N(R¹¹ R¹²),--O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --OCOR¹¹, --CH₂ OCOR¹¹,--CH₂ NHCOR¹¹, --CH₂ NHCOOR¹³, --CH₂ SR¹¹, --CH₂ SCOR¹¹, --CH₂ S(O)_(m)R¹³ wherein m is 1 or 2, --CH₂ NHCO(CH₂)_(n) CO₂ R¹¹, --N(R¹¹)COR¹²,--NHCOCF₃, --NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n) OCOR¹¹ and--NHCO(CH₂)_(n) OR¹¹,wherein n is 0 or is an integer of from 1 to 6,each of R¹¹ and R¹² is independently H or C₁ -C₆ alkyl or, when R¹¹ andR¹² are attached to the same nitrogen atom, they may alternatively formwith the nitrogen atom an N,N-tetramethylene group; and R¹³ is C₁ -C₆alkyl; the pharmaceutically acceptable salts thereof and thepharmaceutically acceptable esters thereof selected from the groupconsisting of branched and unbranched, saturated and unsaturated C₁ -C₆alkyl esters.
 3. A compound according to claim 2 wherein one of R₆ toR₁₀ is selected from hydroxy, halogen, alkoxy, --NHCOR¹¹ --CO₂ R¹¹,--SO₂ R¹³, --CON(R¹¹ R¹²), --NO₂, --SO₂ N(R¹¹ R¹²), --SOR¹³, and--N(R¹¹)COR¹² and the other four of R₆ to R₁₀, are H.
 4. Apharmaceutical or veterinary composition comprising a pharmaceuticallyor veterinarily acceptable carrier or diluent and, as an activeprinciple, a compound as claimed in claim
 2. 5. A process for preparinga compound as defined in claim 2, the process comprising alkylating acompound of formula (B): ##STR22## wherein R₁ to R₁₀ and R₁₄ are aredefined in claim 2, with a compound of formula R₁₅ --X wherein X is ahalogen, in the presence of a base.
 6. A method of treating resistanceto an anthracycline antibiotic having neoplastic activity in a patientharboring a tumour, which method comprises administering to a patient inneed thereof a therapeutically effective amount of a compound selectedfrom the group consisting of a piperazine of formula (A): ##STR23##wherein ₋₋₋₋₋₋₋₋ denotes an optional bond, provided that either ₋₋₋₋^(a) ₋₋₋₋ and ₋₋₋₋ ^(c) ₋₋₋₋ are both bonds and ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋^(d) ₋₋₋₋ are not bonds, or ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋ ^(d) ₋₋₋₋ are bothbonds and ₋₋₋₋ ^(a) ₋₋₋₋ and ₋₋₋₋ ^(c) ₋₋₋₋ are not bonds;each of R₁₄and R₁₅ is independently selected from hydrogen and C₁ -C₆ alkyl whichis unsubstituted or substituted by a group selected from halogen,phenyl, C₂ -C₆ alkenylene, cyano, hydroxy, --OC(O)R₁₁, --N(R₁₁ R₁₂),--CON(R₁₁ R₁₂), --COOR₁₁, a group succinimidyl, phthalimidyl or##STR24## provided that when ₋₋₋₋ ^(b) ₋₋₋₋ and ₋₋₋₋ ^(d) ₋₋₋₋ are bothbonds at least one of R₁₄ and R₁₅ is C₁ -C₆ alkyl substituted as definedabove; R₁₆ is C₁ -C₆ alkyl unsubstituted or substituted either asdefined above for R₁₄ and R₁₅ or substituted by a 4-pyridyl group; andeach of R₁ to R₁₀, which may be the same or different, is independentlyselected from hydrogen, C₁ -C₆ alkyl unsubstituted or substituted by oneor more halogen atoms, C₁ -C₆ alkoxy, C₁ -C₆ alkylthio, halogen,hydroxy, nitro, phenyl, cyano, --CH₂ OH, --CH₂ COOH, --CO₂ R¹¹,--NHCOR¹¹, --NHSO₂ R¹³, --SO₂ R¹³, --CON(R¹¹ R¹²), --SOR¹³, --SO₂ N(R¹¹R¹²), --N(R¹¹ R¹²), --O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹,--OCOR¹¹, --CH₂ OCOR¹¹, --CH₂ NHCOR¹¹, --CH₂ NHCOOR¹³, --CH₂ SR¹¹, --CH₂SCOR¹¹, --CH₂ S(O)_(m) R¹³ wherein m is 1 or 2, --CH₂ NHCO(CH₂)_(n) CO₂R¹¹, --N(R¹¹)COR¹², --NHCOCF₃, --NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n)OCOR¹¹ and --NHCO(CH₂)_(n) OR¹¹ ; wherein n is 0 or is an integer offrom 1 to 6, each of R¹¹ and R¹² is independently H or C₁ -C₆ alkyl or,when R¹¹ and R¹² are attached to the same nitrogen atom, they mayalternatively form with the nitrogen atom an N,N-tetramethylene group;and R¹³ is C₁ -C₆ alkyl; the pharmaceutically acceptable salts thereofand the pharmaceutically acceptable esters thereof selected from thegroup consisting of branched and unbranched, saturated and unsaturatedC₁ -C₆ alkyl esters.
 7. A method of treating resistance to ananthracycline antibiotic having neoplastic activity in a patientharbouring a tumour, which method comprises administering to a patientin need thereof a therapeutically effective amount of a compoundselected from the group consisting of a piperazine of formula (Aa):##STR25## wherein each of R₁₄ and R₁₅ is independently selected fromhydrogen and C₁ -C₆ alkyl which is unsubstituted or substituted by agroup selected from halogen, phenyl, optionally substituted C₂ -C₆alkenylene, cyano, hydroxy, --OC(O)R₁₁, --N(R₁₁ R₁₂), --CON(R₁₁ R₁₂),--COOR₁₁, a group succinimidyl, phthalimidyl or ##STR26## provided thatat least one of R₁₄ and R₁₅ is C₁ -C₆ alkyl substituted as definedabove; and each of R₁ to R₁₀, which may be the same or different, isindependently selected from hydrogen, C₁ -C₆ alkyl unsubstituted orsubstituted by one or more halogen atoms, C₁ -C₆ alkoxy, C₁ -C₆alkylthio, halogen, hydroxy, nitro, optionally substituted phenyl,cyano, --CH₂ OH, --CH₂ COOH, --CO₂ R¹¹, --NHCOR¹¹, --NHSO₂ R¹³, --SO₂R¹³, --CON(R¹¹ R¹²), --SOR¹³, --SO₂ N(R¹¹ R¹²), --N(R¹¹ R¹²),--O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --OCOR¹¹, --CH₂ OCOR¹¹,--CH₂ NHCOR¹¹, --CH₂ NHCOOR¹³, --CH₂ SR¹¹, --CH₂ SCOR¹¹, --CH₂ S(O)_(m)R¹³ wherein m is 1 or 2, --CH₂ NHCO(CH₂)_(n) CO₂ R¹¹, --N(R¹¹)COR¹²,--NHCOCF₃, --NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n) OCOR¹¹ and--NHCO(CH₂)_(n) OR¹¹ ;wherein n is 0 or is an integer of from 1 to 6,each of R¹¹ and R¹² is independently H or C₁ -C₆ alkyl or, when R¹¹ andR¹² are attached to the same nitrogen atom, they may alternatively formwith the nitrogen atom an N,N-tetramethylene group; and R¹³ is C₁ C₆alkyl; the pharmaceutically acceptable salts thereof and thepharmaceutically acceptable esters thereof selected from the groupconsisting of branched and unbranched, saturated and unsaturated C₁ -C₆alkyl esters.
 8. A method of treating resistance to an anthracyclineantibiotic having a neoplastic activity in a patient harbouring atumour, which method comprises administering to a patient in needthereof a therapeutically effective amount of a compound selected fromthe group consisting of a piperazine of formula (Ab): ##STR27## whereinR₁₄ is selected from hydrogen and C₁ -C₆ alkyl which is unsubstituted orsubstituted by a group selected from halogen, optionally substitutedphenyl, optionally substituted C₂ -C₆ alkenyl, cyano, hydroxy,--OC(O)R₁₁, --N(R₁₁ R₁₂), --CON(R₁₁ R₁₂), --COOR₁₁, a groupsuccinimidyl, phthalimidyl or ##STR28## R₁₆ is C₁ -C₆ alkylunsubstituted or substituted either as defined above for R₁₄ orsubstituted by a 4-pyridyl group; and each of R₁ to R₁₀, which may bethe same or different, is independently selected from hydrogen, C₁ -C₆alkyl unsubstituted or substituted by one or more halogen atoms, C₁ -C₆alkoxy, C₁ -C₆ alkylthio, halogen, hydroxy, nitro, optionallysubstituted phenyl, cyano, --CH₂ OH, --CH₂ COOH, --CO₂ R¹¹, --NHCOR¹¹,--NHSO₂ R¹³, --SO₂ R¹³, --CON(R¹¹ R¹²), --SOR¹³, --SO₂ N(R¹¹ R¹²),--N(R¹¹ R¹²), --O(CH₂)_(n) N(R¹¹ R¹²), --O(CH₂)_(n) CO₂ R¹¹, --OCOR¹¹,--CH₂ OCOR¹¹, --CH₂ NHCOR¹¹, --CH₂ NHCOOR¹³, --CH₂ SR¹¹, --CH₂ SCOR¹¹,--CH₂ S(O)_(m) R¹³ wherein m is 1 or 2, --CH₂ NHCO(CH₂)_(n) CO₂ R¹¹,--N(R¹¹)COR¹², --NHCOCF₃, --NHCO(CH₂)_(n) CO₂ R¹¹, --NHCO(CH₂)_(n)OCOR¹¹ and --NHCO(CH₂)_(n) OR¹¹ ;wherein n is 0 or is an integer of from1 to 6, each of R¹¹ and R¹² is independently H or C₁ -C₆ alkyl or, whenR¹¹ and R¹² are attached to the same nitrogen atom, they mayalternatively form with the nitrogen atom an N,N, tetramethylene group;and R¹³ is C₁ -C₆ alkyl; the pharmaceutically acceptable salts thereofand the pharmaceutically acceptable esters thereof selected from thegroup consisting of branched and unbranched, saturated and unsaturatedC₁ -C₆ alkyl esters.
 9. A method according to claim 6, 7, or 8 whereinthe anthracycline antibiotic is doxorubicin or daunorubicin.
 10. Amethod according to claim 6, 7, or 8 which comprises administering thesaid compound to the patient whilst the tumour is exposed to the saidanthracycline antibiotic.